Better indication of logged-out client

[Rello]

If the apptoken is revoked for a valid reason - e.g. due to a password change in Nextcloud - the desktop client stops syncing.
The task bar icon changes (e.g. to grey on Windows) but it might not be immediately visible to the user.

Better alternatives like e.g. notifications should be evaluated

[Mika-6-9]

Hi
Until version 3.12.8 there was a very useful notification (#5036) which has apparently been removed from version 3.13.x (#6994).
Did it also work on user logout, I don't remember.
It would be nice if this feature came back.