Thanks for this information. It is a bit advanced for me but I'm certain other people here can do this.

Thanks NotaTether I think this is important to know.

Thanks everyone for all of your help to gain understanding of this.
Electrum has a lot of features to learn.

Can anyone tell me the command to see all addresses in my wallet that have received coins.

Listreceivedbyaddress 0 true does not work. It does not show addresses I know that have funds on because the overview shows those addresses receiving coins and the total balance.

The QT overview shows the correct balance. But now I've restored from an older wallet.dat. All receive addresses I made after this backup seem hidden or just vanished. This is very strange and a bit worrying.

Is there a command that just shows every address with coins on inside your wallet.dat?

Edit 2/ after lots of googling I find this is a known issue or bug.


https://github.com/bitcoin/bitcoin/issues/20293

https://bitcoin.stackexchange.com/questions/88434/listreceivedbyaddress-missing-transactions-after-restore

So although listreceivedbyaddress does not show these addresses have received coins because of some label issue
Does it matter? I mean the wallet.dat seemingly does not acknowledge these addresses at all or has no label for them but can still spend from them?


Edit/ it seems if you make a new wallet.dat make 1 recieve address send bitcoin to this address.
Then make multiple copies of that wallet.dat as backups.

Now if you make more receive addresses and send coins to them after a time and your machine breaks.

When you go to your backup wallet.dat and reload into a new qt wallet.
Those new recieve addresses that have recieved coins. Will never appear.
Like if you keep clicking generate new receive address it will skip past those that have recieved coins.
If you type type listreceivedbyaddress 0 true or listreceivedbyaddress  1 true
It will never show those addresses? However it will show the original receive address and the initial coins you sent to it.

This is very strange? It worries me I can not seem to make the qt demonstrate I still control those addresses.
Its like they just never existed. Although you can see the tx shown on the overview page of the qt ?


https://bitcoin.stackexchange.com/questions/88434/listreceivedbyaddress-missing-transactions-after-restore

Edit3/

Okay so eventually I solved this and I will relay what I found here for others just because it may happen to you.

When you restore from and older wallet.dat file sometimes all the new received addresses you have generated on your more updated wallet.dat are for some reason now labelled as change addresses so are kind of invisible to a novice user.

This causes some strange things to happen.

Listreceivedbyaddress 0 true will not show these addresses

When you generate new receiving addresses these addresses even if unused will never show up so it seems that it is making different addresses in a different order to a more recently used wallet.dat. Depending on how many new received addresses you made on the more recently used wallet.dat before then resorting to restoring from an old wallet.dat you may need to create lots of new addresses before you see them creating the same exact addresses on both machines.

To see them and check you still have these addresses under your control in this wallet.dat
You can simply click on coin control and then under the send tab click on inputs

This will then show you all of your addresses and all of the coins on those addresses.
So now you can relax. The coins are still inside that wallet.dat and you can spend them.

I am not sure why this happens but maybe it is not a bug it is just a bit confusing to a novice.
1 moment these were receiving addresses you could see and next moment these are invisible change addresses.
But no matter you still have control of the coins.

1 slight issue may be if you wanted to dump priv keys and you forgot about the change addresses.
So coin control can be used to check.

Thanks that was very helpful I see exactly what you mean.
I am going to use coin control for all tx in the future I think.
I can just add more uxto (coins) to the coin control as required.
When you add a coin or uxto to coin control does electrum remember that next session or you need to re add and reference dust attack coins each time?


Does anyone know why electrum is set up to use all input uxto on the same address? Even when just 1 input uxto has sufficient funds to make the spend?

This is very strange default isnt it?
Or is there a reason ?
If you set up a watch only wallet using only a single public address not xpub
Then change is always sent to that same address. Not a different change address.

So can anyone explain why if you have 40 uxto each having more than the single spend amount. Why electrum wants to use 40 inputs?
It could use just 1 uxto input.

Is there a reason specifically related to a watch only single address wallet?
I suppose after the first time it moves all of you coins from all of the 40 uxto and then send the change to the Sam's address , will that be in 1 big uxto clump? So only the first time it spends with a huge tx fee and the following times it will be just a single input and be much cheaper tx fee?

Is the reason electrum uses every single input when it could use just 1 input because it is attempting to organize or consolidate your uxtos?
Or is that not why electrum does this?
Thanks.

Edit /

Thanks promise444c5

This is true. I think electrum always wants to spend your entire balance even for a tiny spend and then send you all your change back usually to a new address for privacy and security.

This is very expensive in fees right now and if you have a watch only wallet created from a single public address then the change can only be sent back to that address. So it seems crazy to pay for 40 input uxtos rather than just 1.

Is that correct ?

Are there issues you can create using coin control with watch only wallet on a single public address?
I just wondered why electrum does not default to using a single uxto input for a spend in this case.
Thanks for everyones information. Very helpful.
Does bitcoin core auto use all uxto and send the entire balance of an address then send the change to a new address also or is that just electrum?

Thank you for the idea.

So you think I should put a tick next to ^ spend only confirmed coins ^  this will stop electrum trying to send out any unconfirmed low tx fee coins I will eventually receive? I dont need to use these and prefer to let them confirm before spending them. I don't want to mix them in the send with my confirmed coins.

You touch on an interesting point with coin control in electrum.
I have noticed that I set up a watch only wallet with electrum using only the import a single public address way.
This way it always sends my change to the same address that im sending from.

However. For some strange reason. If I am only spending a tiny amount of btc. Electrum wants to use every single input to that address.
This is unexplainable to me because each input uxto has enough alone for the small spend. Why would it do this?

Why would electrum choose to use every single input when 1 alone would suffice?
I noticed another guy asked this and when I checked it is happening to me also.
I am paying huge fees for very large tx size when I'm sure if I use coin control I can select to use just 1 input uxto. Not loads of inputs.

Is there a danger of doing this using a watch only wallet that spends the change to the same sending address?
I have not meddled with coin control before. Are there things to be wary of?

Thanks for any insight.


Replying to Charles-Tim.

these small dusting attacks can be dangerous?
What can they do to a watch only wallet behind t or

Thanks

If people send you some bitcoins but use a low fee It can stay unconfirmed for a long time.  You dont actually have those coins yet.

If you want to continue to spend and use your fully confirmed funds without mingling in these unconfirmed funds is the best way to ensure there is a tick next to the option ^ spend only confirmed coins ?

Will making sure that has a tick next to it

A/ stop you spending any of your coins until these coins sent to you with low fees confirm fully

Or

B/ electrum will ignore those low fee unconfirmed coins and just spend from your confirmed coins?

I am wondering why it is unticked by default? I see someone sending me some bitcoin with 5 sats fees.
That will likely not get confirmed for a long time so I dont want that to mess up my confirmed funds.


So if I put a tick next to the spend only confirmed what will happen A or B.

I assumed B but seeing the tick is not there by default made me doubt and I cannot find the exact answer.

Thanks. 

Thanks for your help .

Actually this is very strange.

I tried that command in both machines .
Listreceivedbyaddress 0 true then it shows
Both machines came up with the same address starting with 1 the legacy address with funding of the same amount.

However machine 2 came up with the address starting with 3 at the start with more coins inside?

But this seems so weird because on both machines the gui front page on the wallet shows received coins to the address starting with 3
Address.

Can sometimes addresses be missed out of a wallet.dat?

But if it was missed out how can the gui show it on the wallet front page ? I see that address starting with 3 on both wallets. Even though it is not there when I do the listreceivedbyaddress 0 true command.

Can a wallet dat saved at a different time miss out an address?
But if it did why would it show on the gui it received coins to that address on the wallet front page?

Machine 1 the most recently synced one shows coins recieved to an address starting with 3
But that command listreceivedbyaddress 0 true does not bring that up in the console.

Thanks. Yes I didnt explain well.

No, I've not tried multi sig.

I think the problem was that the wallet on machine 1 with a more recent blockchain could see that several addresses had been used to receive coins. So it had hidden them from view as recieve addresses. Machine 2 with a older copy of the blockchain didnt know this so was generating them as new receive addresess. So it looked at first like they were not generating the same sequence of addresses

So it took a few more clicks on both until I reached an address that had never been used to receive coins.

They are now both creating identical addresses in the same order on both machines.

I wasnt aware bitcoin core hides receive addreses once they have been used.

Thanks for replying.

Okay a few updates and details. I think I perhaps found out what was happening.

Machine 1. Not internet connected but blockchain updated in the last few weeks. Running bitcoin v21
Machine 2. Not internet connected blockchain now out of date by over a year or more ..(But blockchain was not even on day 1 and said 15 years behind when I wrote the first post).

Both have the same wallet.dat or if not the same wallet.dat exactly then an older copy of that same wallet.dat.
Because both show the same received tx on the gui front page. Slight different balance because a couple new tx have shown up on machine 1 because it has a more updated blockchain.  

Confusing things to me.

1. When I load this wallet.dat into machine 1. I see the same balance (pretty much)as machine 2 even now.
But although machine 1 shows in the transactions it has received to an address starting with a number 3 previously.
When I click on the tab in core that says window and go down to receive addresses.
That address 3 is not there I see different addresses.

When I look at this receiving addresses list on both machines then I see this.

Both machines match with the first address this starts with a 1
But then machine 1 does not have the receiving address starting with 3. Machine 2 shows this address.

Then when I was clicking generate more receiving addresses they were creating different addresses even after I noticed  a matching 1.
This matching address started with a bc1

Now that I've loaded a more updated blockchain to machine 2
And generated a lot more receive addresses I see they are all matching.

What I think happened was this. I'm just guessing.

I suspect that machine1 is removing addresses that starts with a 3 or bc1 as receiving address once it has some bitcoin sent to it.
So I had to keep making more and more until it got past those that machine 1 could see had recieved some tx but machine didnt know had received coins already.

The thing that seemed strange to me at the time was this.

Machine1 eventually produced a recieved address I could see that machine 2 had on there. But because machine 1 knows the next 2 addresses had already recieved coins ...then when I pressed generate more. It skipped those.  Where as machine 2 did not know this and produced them.

When they started producing the same addresses. Then when I went back I could see aha these addresses that machine 2 was generating had actually recieved coins on machine 1 in the past but those addresses machine 1 had taken out of the recieved address preview window.

I think there may be some settings somewhere where you can tell bitcoin core to show you all recieved addresses even if they had been used to recieve previously.

Strange thing is that it leave the address starting with 1 even though that has been used.

Maybe this is reasonable explanation?

Thanks.

I have a strange occurrence I dont understand.
I have an old wallet.dat file I am scanning all my old usb drives.
I loaded it into a bitcoin core wallet on 2 different machines running the same version of bitcoin core.

The weird thing. On machine 1 I see different receive addresses to that on machine 2.
On one machine I can see the wallet has received coins to an address starting with 3
But that is not even showing up when I click receiving addresses?
How can that be possible? How can an address the wallet show received coins into it and those coins are still there are not listed under the windows receive addresses tab? That seems impossible?

Also when I click generate new receiving addresses 5x and got 5 new addresses on each machine.
Only 1 of those addresses  5 matched on both machines the others were all different . ?

This seems weird because I was expecting these wallets to generate addresses that matched in the same order?
Is this not how it should work? Even after they both generated a matching address. The next ones were different?
I was under the impression bitcoin core knows the next address to be generated even if it is offline? So I was expecting them to produce the same matching addresses in tandem.

Is one a rogue wallet generating rogue addresses it should not generate?

Electrum generates the exact same addresses in the exact same order if run on 2 different machines?
Does core not make them in order?

How to see every single address that a core wallet currently controls or has had some action?
Sorry this bit is also confusing.
Listaddressgroupings command does not tell you the addresses your wallet.dat controls?
It tells you what people may think you control?

This is strange

Which command to put in bitcoincore to make it show every address it controls and its balance?
This should total the same amount of bitcoins that the wallet gui shows is inside it ?
Is that correct.

Listaddressgroupings does not show you which addresses your wallet.dat controls this is just on chain analysis and guess which wallets are related somehow?

What about this command - listreceivedbyaddress add a true of false on the end?
What does the true and false bit mean?
I just want to see every address in the wallet I control with my wallet.dat and every address with how much is contained on that address.

Yeah, I'm not certain what it means about the fees being later maliciously adjusted.

Seems strange.

Does it mean.

A. If you had 10 bitcoins in your wallet someone could charge the entire 10btc in fees
Even though only want to send 0.01btc to the recipient and want to spend 0.0002 in fees.

B. That when you have signed it to allow 0.01 btc out of your wallet then it could just use up that entire amount in fees.

I dont actually know what it means.

I dare not test it with a small tx because it may mean it can absorb the entire balance and use it as fees.

When you look at a raw signed hex in bitcoin core wallet with the decoderawtransaction command.
Where do you see the fees?

I can only see the vout for the recipient and change.
I don't see on the bitcoin console where it shows the fees.

I believe someone said you can just calculate that when you take the recipient and change from the balance.
But on electrum it shows the fees in the console expressly.

I'm not sure why but the yellow triangle just seems to be worrying.
It says it can only be maliciously changed until signed. But I'm signing it straight away.

Thank you yes .


That only applies to exported fully signed raw transactions.
Even the file export (.txn) shows the same hex characters when opened as text.

If unsigned, Electrum will export it in PSBT format, via save to clipboard (base64) or file export (.psbt)


Ah yes you are correct it only works on the signed tx. Thanks.



Cold-storage Electrum setup supports QR Code export and scan,
That essentially fulfills your main goal to eliminate the usage of flash drive in your setup

Yeah I'm confused why I get a warning that qr code can not contain all the data of the psbt unsigned tx.
When I scan it on the airgapped machine it gives a warning yellow triangle says cant put the fees and it can be maliciously changed.

When I transfer on usb it works fine and no warning.

Is there any particularly reasonable explanation why you must use Bitcoin Core in your Air-Gap machine instead of another offline Electrum?

Well only that I was wondering if I could avoid doing a dumprivkey to core to put that into electrum. The wallet.dat was made in core and even a key logger could only see my passphrase to sign at the moment and I think if it could slip out a passphrase hopefully it could not slip out a wallet.dat

I'm able to scan qr code for signed as it seems all the info can easily fit inside.

So I can use the airgapped electrum but at the moment I still have to bring the unsigned psbt with usb so I guess there is some danger something slips in to the airgapped machine.  

I probably shouldn't use that usb again even though I do format it straight away as soon as I used the psbt from it  

Someone suggested to me you can break the unsigned data into parts and make several qr codes but I got lost on his idea.

Thanks for pmalek also for warning about possible issues in the future I will work on a way for electrum only until broadcast rawtx at then end from full node.

Thanks nc50lc for taking time to make this excellent guide.
I hope other people who want to move funds from their offline wallets and dont know exactly how to make the descriptors code can also find this guide very simple way to spend some of their funds.

Using electrum watch only to make the correct inputs outputs and fees for a tx
Then input to bitcoin core ( so dont need to go through all the dump priv key or even install electrum on offline machine if they dont want to.
Then sign with offline core wallet. Export signed tx and can spend on watch only electrum or on a synced up bitcoin core.
Sounds good.

I

I may do another experiment using clipboard and not using files with bitcoin core.
Because I notice with electrum when you use clipboard outputs and not save to files.
This keeps everything in hex. Which is just numbers and letters.
When you save to files instead it adds extra symbols like//++ other stuff I think psbt is an unsigned tx but with some different way to code it.

The nice thing about just hex is that if you break that long hex string in 3 and fit on one page without sideways scroll.
You can take a picture on your phone and depending which phone you have it can turn that picture into a text file.
So you dont need to transfer anything physical off from the offline machine.
Just a photo. Then use phone to turn back to hex file with built in OCR.

So you can then type decoderawtransaction in bitcoin core to check all the details
If it looks good then sendrawtransaction.

This could be a reasonable solution for the novice who wants to move some btc from offline machine that just has bitcoin core but no electrum already installed there.
 
This process only requires the skill to download electrum to an internet connected machine and copy in the address you want to send from to make the watch only wallet. Then make a send tx and save to psbt file. Take that on usb to you offline machine and load psbt into core.
Sign it and save as file, to transport back to the online full node to broadcast, or broadcast on electrum watch only to broadcast.

Some people say it is unsafe to USB files on and off a airgapped machine. Because sometimes inside the usb bios can be a virus. You can't even see it on the files of the usb. Even formatting cant always remove it.

So perhaps 2 ways to mitigate this I have been thinking about.

1. You can usb on to the airgapped machine the psbt from electrum but then format that usb or even chuck it away if it is just a couple dollars small usb.  Then take a photo and OCR on phone of the signed raw hex output, to test by decoderawtransaction. Before sending.

2. If you're great at touch typing of have a lot of bitcoins then you may even consider
If it is possible for you to export the unsigned tx you made in electrum not by a file but by clipboard and get in raw hex.
Then copy it by just typing it all into your offline machine. Dont make a mistake though.

That is if you really dont want any single physical contact with usb or anything with the airgapped machine.

I have not tried 2. I'm not to great at typing without looking at the keyboard.

Also Zaguru12

Thanks it's good to know they need password and dat file.

This information makes me think signing with core on airgapped machine is safer than importing priv key to electrum.
Because even if a keylogger could sneak the private key out of the airgapped machine or the password encrypting the dat file on a qr code. I dont think it can sneak the wallet.dat off this way.

If anyone can notice any problems with my process then please say.

Perhaps you have now revealed a reason some says yes and some say no.

2 persons have said it is fine to load electrum generated  psbt into bitcoin core.
And 2 have said this can cause problems but didnt say why or what problems.

Maybe that explains the reason.

Those that tried it and said it works fine perhaps only used the very latest version?

I don't want to touch the airgapped machine at all so installing the very latest bitcoin core is not something I can test.
I want to test this on the v21 but I wonder if I can cause some issue that I can then not rectify after.

I suppose I could try it and compare the signed output hex with the hex signing on an electrum wallet produces.
Then if both are exactly identical it is proven to work with zero possible issues?

Or am I still missing deeper potential  issues?

Hi, I would like to understand a little more about the bitcoin core wallet and if it is cross compatible.

Is it possible to create a watch only wallet in electrum . Feed in the public address of a bitcoin core cold wallet.
Create a psbt with the electrum watch only wallet and save to file.   Then where it says load psbt file in bitcoin core v21 just load in that electrum generated file?

Is that dangerous or perfectly fine and long as the change address is the same as the sending address?
Are psbt created with electrum cross compatible? Some people say yes some say no. I don't know who is correct and I can find no mention of importing an electrum watch only wallet generated psbt file into a bitcoin core wallet.

If that is possible and you can sign on the airgapped bitcoin core wallet you can then somehow export the signed tx in hex format and send on the internet enabled full bitcoin node?

I just want some others opinions on feasibility of this process.

Also, this may seem a strange question. But when you create a bitcoin wallet years ago then you also encrypted it with a long password.
If someone only has that password but no access to the wallet.dat file then your coins are safe even if they have the public address?
How can keyloggers steal peoples bitcoins if they can see the password you will type but they can not grab the wallet.dat file?
Or do keyloggers also easily take that wallet.dat file off your machine easily?

Thanks.

Thanks for explaining. Yes I am more relieved now I know it will simply keep returning to the same address.

Thanks, yes I agree about the virgins that might say this are incorrect.
So i dont have a cold wallet or airgapped wallet really.



I don't know why that is. Sorry, can't help you there.

It seem to be because too many inputs and I have to use coin control
To make less inputs ifI can work out how. Then the qr code will work.


I don't know why you would go through this trouble of setting up a third device and testing the transactions like you are planning. What do you expect will happen if you don't carry out those tests

I was a little bit worried if there was a malware lurking on the old laptop or if I did put one there with the usb stick by mistake.
Then I could be shown in the preview what looked to be a good transaction and I click sign. Then export the qr code but actually it was a qr code sending my bitcoins to a hacker. It is hard to see what is inside that qr code. I would think the watch only wallet could reveal it was a bad qr but maybe it would send or something would be revealed in that QR that was now getting to the internet.

So I thought maybe load that qr code with the signed tx into a 3rd offline machine with electrum and make sure the preview looked good.
Then if that looked okay then load it to the watch only and send it.

It could be unnecessary but only takes one second to scan that qr to the 3rd offline machine.

Or rather I might then use the watch only to see the hex of that qr code and send that hex with bitcoin core full node.

When people describe how to make a totally safe airgapped wallet from scratch perfectly it seems beyond my skills.
Even a brand new laptop they say sanitize the bios, remove wireless, make sure install totally safe and checked operating system again without usb or some internet seems impossible to me. Then all the new softwares or making my own private keys without any software like bitcoin core. I thought get a trezor or cold card but I still have to get the coins off that old laptop and sent to a trezor.
Then some people they dont like hardware wallets for various reasons, some which do make some sense.

  I think I will make more mistakes than just maroon this old machine  and try to limit anything on or off except qr codes and the odd input with usb where qr code is overloaded. Once I learn to

Thanks I see that I was calling my wallets cold wallets and airgapped wallets
But they are not cold at all. Maybe they are airgapped? Or maybe they are not airgapped either.

This laptop where they are stored both electrum and bitcoin core. Was once used with the internet.
It has not been turned on or connected to the internet in over a year or more. Maybe 2 years.
I checked the block explorers ( from a different machine) and the balances were still there.
I was worried it may not be sensible to ever connect that to the internet or allow it to connected with anything at all even usb.
Because nothing leaked off it yet but in future?


So I decided to make this laptop my " cold wallet" ( I understand this is not cold now) taking out my wifi card, deleting the bluetooth and disabling it and never to put the ethernet cable. Also put on airplane mode.

So i thought this machine is now airgapped nothing in and nothing out except a qr code from electrum only.
So yes I guess this isnt a cold wallet but it is now airgapped? Nothing physical touches it and no internet capacity.


That was my plan. But sadly the qr code from the watch only machine  cant contain enough info for the psbt.
This is a big problem.


So then my plan was okay, I will allow usb with the psbt into the airgapped wallet only because I have no choice. Then format it each time.
But only allow qr codes for the signed.txn out of the airgapped machine no usb out.

I though well if I only allow qr codes out from the airgapped machine then test before submitting  then what issues can happen?

Even if I did transfer a key logger into the airgapped machine then surely as long as the air gapped machine only outputs an electrum qr code ever and nothing else it should still be okay if that usb was then formatted on air gapped machine before using again


So I have my signed.txn qr code and I want to test that before broadcasting.

So I set up a 3rd laptop with electrum. Also offline, to scan in the QR code and see if the inputs out puts look okay. Just incase the watch only wallet shows me fake info or just auto broadcasts before I can detect it is about to scam me. I just want to read that qr code in human readable text before I load it to the watch only wallet. But it seems impossible to read it.
Someone said you can make it to json to read it but I dont know without using 3rd party software.

If the 3rd laptop (offline electrum just to check)  looks okay and all checks out the I know the airgap generated qr code is probably good.
I can also then test the qr code on the watch only electrum, that is running a different version of electrum downloaded at a differ time.
If that shows the correct inputs also.  Now I'm very sure this is a good signed.txn qr code. Correct?

Now I could broadcast that with the watch only wallet, but i want to broadcast on my own core full node. So more steps.

Sadly the qr code is not accepted by bitcoin core so this needs to be made to hex.

To get the hex I guess I can either use either laptop 3 or the watch only to reveal the hex of the loaded qr code. I have not tried this yet.
Or take the hex from the airgapped electrum which signed it ?

I just didnt want to touch the airgapped machine at all with usb at any point. So to get the hex off this airgapled machine without usb is an issue so i hope once I load the qr code of the signed.txn into the watch only then I can press some tab to reveal the hex that was contained in the qr code.  

If not damn.

If that does not work I can still get the airgapped machines signed.txn hex code perhaps by taking a photo of the screen in my phone and using the special select feature it turns text in images to text you can use to save to a file or just email to the machine running bitcoin core to broadcast the rawtransaction.

I could rename this thread how to get bitcoin off a machine without the internet or usb ,but I guess this would work the same for cold wallets in airgapped machine.

I suppose I got unlucky with the psbt being to large for the qr code on mine other people probably can never touch their cold or airgapped wallets physically. And can do the entire thing with QR codes.

Also most people may just be happy to broadcast their signed qr with electrum and not want to decode it to hex to send on their core node.  

So Its a bit more steps for my way to keep my old machine free from usb and internet totally.
Only communication via camera or keyboard is desirable.

I will change the title.

Thanks I've realised then that you can not start the spend from the cold wallet on the air gapped machine.
I thought I could do that.

Import the key from where? You are going to create a new wallet on your airgapped system. That's where you generate your seed and the private keys. Don't import a private key from somewhere else. It's not going to be a key you created in an airgapped environment, unless it came from another cold wallet

I should explain my bitcoin core with a bit of a bitcoin and my electrum with a bit of a bitcoin.
Both are on the same airgapped machine. So maybe just to dump the priv key and import to electrum will be okay so long as camera cant see it. Because these wallets have some tx histories I think it maybe possible to start the send tx and sign from the airgapped machine.

However, if that is not possible.  You have made me realise that If the QR code can not contain the full information of the psbt generated by the watch only wallet. There are just 3 choices. To use a usb. To ignore the yellow triangle  warning sign saying fees can be maliciously increased or copy the psbt by hand to the airgapped machine.

I think the qr code can always contain enough data for the signed.txn
So that is one good thing.

But from what I can find out there is no way to keep the laptop fully airgapped if the qr code can not contain the full data of the psbt from the electrum watch only wallet. Not for a novice.

For an advanced expert it would be possible.

I guess it does not make a big difference because if the airgapped wallet ever only outputs a qr code from electrum then it would be unlikely to leak anything dangerous.

Just a shame you do have to plug a usb at all to the airgapped machine with the electrum psbt process.

Thanks for the explanation of the uxtos and addresses.
I guess it is very dangerous for the untrained to make assumptions in this field.
I had though if always sending and receiving to the same address you could not have to worry about which input uxtos specifically.

I started a specific thread for this idea only. To get critique from experts on a process to spend as safely with a cold wallet as you can.
Maybe other novices can use this thread after experienced users say it is going to work.

I'm a novice user trying to understand this but I see on reddit so many people wanting to achieve this. But they get stuck on setting up electrum servers or worrying about connecting to a malicious electrum node or set of nodes. Or stuck because their qr code is not large enough to contain the information from the psbt,  but they want to remain ice cold.

I want my cold wallet to remain 99.99% cold as possible.
No physical connection with usb or any input at all except my own typing or qr code at worst.
Output I prefer only QR code. No usb extraction if I can.
Would like to broadcast on my own bitcoin node if possible.

This could be ideal for when you get an issue where the qr code can not contain all the info from the psbt. Then you need to go usb but dont want to.
I'm not sure of any hardware wallets that you can import a priv key, and you dont trust hardware wallets maybe.

Option A -  perhaps could work out? Or a possible issue? How to select appropriate fee?

Forget psbt? Maybe this is easier if your qr is too large to work.

1.import private key to electrum airgapped
2. Look what address appears.
3. Set up electrum watching wallet for that address only  on other internet live machine see balance.
4. On airgapped wallet select spend but untick use new change address ( this is because if I'm not wrong the drawback with starting on an airgapped wallet is it doesnt update its memory of prior tx until you submit and it gets confirms which it cant do airgapped.
But at least getting all change to the same address. You can keep spending from this cold wallet until you know it is all used up. Or can you? Are uxto the same as addresses? Maybe even when change is issued to the same spending address. There can still be an issue starting a new spend from a cold wallet? This I dont know right now.  
5. Export the signed tx with qr code.

At this point nothing has been put on the cold machine only a qr code taken off from it.

6. Spend that qr code with the watch only electrum, or if want to spend on you own bitcoin full node see 7.
7. You have a qr code but electrum encodes it with some other format. Maybe to save space and pack more info. Or maybe to make sure electrum only can read this qr code. You can not easily see the hex code that you see if you save a signed.txn on a usb stick. To see this
Hex code you need to spend with bitcoin core. Some person made a website electrum43 to decode that signed tx QR code to hex format.
I am guessing there is a way that an electrum watch only wallet can scan this QR code and you can look at the hex version there and save to a usb or maybe you have that on your same machine with bitcoin core full node running.
8. I believe it is possible to spend that hex directly on bitcoin core wallet with a command like sendrawtransaction or some other command. If you can figure that out you could test the hex code from that QR code one time on your watch only electrum but dont submit. Then if looks good go to blockstream pushtx site and send from there at least their node would not be malicious but you lose privacy so use a burner phone if that is an issue you dont like.

All done.

*4 is seen as a little bit unsafe taking the security from 256bit to 160bit think I understood so not good for long term storage.
I think this can be maybe avoided by clicking save tx to history but I dont understand that enough to know how that stops a possible attempt at spending from uxto that maybe dont have sufficient funds in the future? I think it would work if you only ever used the cold wallet on that machine and not a different cold wallet with the same private key.

This is the tricky part to understand as to how you start a spend with a cold wallet not start with a psbt from a watch only.
The second part is the fees. I guess just look at the network congestion and put a good fee.

Is there any safer way for a novice to spend from a cold wallet or paper wallet where the qr codes cant contain all the information of the psbt from the watch only wallet?p
Are there issues with this process?

On the other hand so to speak

One expert did say this entire idea was a convoluted mess, and if you are happy to have change return to the same spend address. You can just spend and sign on an offline airgapped bitcoin core wallet and copy the hex over to spend on a synced up full node push with blockstream push tx. But he didnt have time to explain how get this hex off the airgapped machine without usb.

So can anyone give the critique of my plan. Or suggest a better way for when qr codes dont work.
Is starting a spend from the air gapped unsynced wallet always a bad idea that can cause issue with attempting to spend from uxto that are now empty? Should you always go with a psbt from a watch only?

Spending from a cold wallet seems a bit tricky fully airgapped for a novice when they hit this qr code space limit on the psbt.
Also spending signed qr code from electrum on core can be a bit tricky too due to it having to be decoded. But I expect the watch only can show that qr hex in some option.