So are like actually linking Electrum with your Trezor (a new option?)? Or is it just like in Ledger Nano S where they import the wallet's public data (public address, amount, transaction etc) to their Ledger Manager software so you can see and watch fund without the Ledger Nano S?
My apologies I can't answer your question if its a new feature. Still new to this bitcoin and learning. Yes you have to have the device connected before you can spend your coins with electrum. Currently I have it set up as it having to be connected just to view electrum wallet and spend. As HCP has mentioned you can create a "watching only" wallet which I will try out.
No, it isn't new feature... it has been available for a while.
And sorry, I forgot to mention... to have the option to use the "watching-only" wallet, you have to connect the Trezor to Electrum and
create the wallet WITHOUT using wallet file encryption. When setting the wallet up, you will get this window:
If you leave it encrypted (default option), as the dialog states: "You will need your hardware device to open your wallet."
However, if you disable the encryption (note: this only affects the wallet file created by Electrum... and
this file does not contain any private keys or seed information... it only has public keys), you will be able to open the wallet without the device connected and be able to view addresses/transactions etc. (== watching-only wallet)
My confusion was that I still had to send my coins from my trezor device to the electrum device before I could spend because of bitpay. Which defeated the point of having a hardware wallet other than for security. Maybe I did it wrong. So please don't take my comments as 100% certain. I like to learn by making errors.
Yeah, you should not have sent any coins from Trezor to Electrum... you should have been able to spend your "Trezor coins" using Electrum. If you actually created a unique wallet in Electrum, then sent coins from Trezor to Electrum, then spent these coins from Electrum... That would be completely the wrong way!
Or, it is quite possible, that because Electrum defaults to searching for a "Native Segwit" wallet when you setup a hardware wallet, that you were just looking at an "empty" wallet
on your Trezor... and, in effect, all you did was actually move coins from one "section" of your Trezor to another.
Without being privy to what exactly you did... and the addresses/wallets involved, it is very hard to know for certain... but my understanding is that Trezor generally only uses "Legacy" (addresses that start with a "1")... and "Nested SegWit" addresses (these will start with "3").
However, when creating a hardware wallet in Electrum, it defaults to "Native SegWit":
If you left it on this default option... you would get "bech32" addresses that start with "bc1"... this is technically still a wallet controlled by your Trezor device (so uses same 24 word seed mnemonic and private keys etc and they're NOT stored in the Electrum wallet), but is NOT the same as the wallet and addresses you would see if you used wallet.trezor.io interface!
To see the same wallet as wallet.trezor.io, you need to select either the "ps2h-segwit (p2wpkh-p2sh)" option... or the "legacy (p2pkh)" option... or create both, depending on how you have been using the Trezor. For instance, I had Trezor before SegWit was implemented, so I have both Legacy and SegWit wallets.
Clear as mud?
But, hopefully that does help clarify things a little bit... I know it can be a bit confusing at first!