Sorry, but that's still so vague.
Anyway, is this what would help you?
Issue 2112 – Warn when opening binary files in internal editor
If it is, you can vote for the request.

The application freezes when trying to read a remote file larger than approximately 1 MB.

When you accidentally click a binary file, the entire application freezes right away.

WinSCP displays a warning, when you try to open a file over 100 MB in the internal editor. Or do you mean something else?

I separated the threads, I don't know why you combined two different topics?

Please add a message about trying to open a large file.

Sorry, I'm not sure I understand. Are these two separate issues/requests? Can you elaborate on both (if they are indeed separate)?

Deactivate only the card with a disconnected device.

Now, when the connected device is gone, you can't even browse the local disk open in the second tab.

Warning before trying to open a large file.
Now the thread is gone, and if you click on a large file, the application freezes and cannot be canceled.