this is it. the solution. it even solves the problem with the "i click onto a folder and looking at old mails, because the scrollbar is in the middle"well it didnt fix this, but at least the menus are now usable again.
I am on Thunderbird 115.4.2 and got the very same issues described here. It just botheres me all the time. i got 7 mailboxes with TONS of folders and filtering rules. Worked great all the time. Now i need to send a bill for a new mouse wheel to mozil...