Bitcoin Forum

I have this window:

https://imgbox.com/51QNpdJ3

But if I add address, it appears till closing of app.
When I open app again, the list of addresses is empty.
Then if I try to add the same address - I get error message that this address already exists - even when the list is empty.

Isn't it a bug?

Not 100% sure what you are looking for.

The screen you are showing is for addresses you have sent TO ALREADY it has nothing to do with YOUR receiving addresses OR addresses you added to send to later.
Under Window (Okno) you should have receiving addresses which are the ones that you can receive. And sending which are ones you added to the "address book" so to speak.

Once you send to them they should appear in the window you are showing.

-Dave

Have you tried to check if the search URL is correct because it looks like a site you've visited before?.
Uhmm,try re-opening that address in another server or webpage because most times,that particular app doesn't support that address just as the forum ejects some phishing links (even though phishing wasn't your prior motives)  
 
If it's an app, contact the developer option!
Sandra :-*

It's an error in Bitcoin Core, not in a browser or a website.

I've tried to manually add an address to the "previously used address" list in the 'send' tab and it persists even after closing Bitcoin Core.
It's the same list in "Window->Sending addresses".

Tested in Windows10 PC - 18362 | Bitcoin Core version 23.0

Maybe it's an isolated case?

Yes, that's strange, that I cannot see the addresses in this window.

Since it says "already exists"; it must really be in the list but the GUI is failing to display it.

You can try to enable debugging with qt flag and check if you can find GUI errors related to the issue in your "debug.log" file.
e.g.: bitcoin-qt -debug=qt

Qt flag didn't helped. No messages in debug.log about that. Just added one address and there was message, but no other messages noted.