I'm using "PhpStorm 2021.2 Build #PS-212.4746.100, built on July 28, 2021" and seeing this button:
I'm also seeing it in projects which are by itself libraries (like in the above example) where it doesn't even make sense and it annoys me / creates noise in the interface (especially since it seems to appear after some seconds entering the editor, i.e. becomes visible/hidden, even further distracting me).
How can I disable this? I tried searching the settings but can't find anything: