Thunderbird shows number of received Messages in DTD

Support Software & Applications
1

– GNOME / Wayland –
Since latest Thunderbird there is a red borded number of received messages
at the upper side of the Thunderbird icon using Dash To Dock…

How to reset - number stays even if message has been read.
Any solution to avoid logout/login circle to reset “the message”?

The thing is called: notification badge counter

2

That is simple:
open extension Dash To Dock.
unselect “Show icons emblems”
BUT: only cosmetic solution…
mentioned already: