This is a weird bug in Catalina, related to an external mouse. If you try the same menu responsivity test with the trackpad, then it’s OK and everything’s insta

This is a weird bug in Catalina, related to an external mouse. If you try the same menu responsivity test with the trackpad, then it’s OK and everything’s instant. Basically, everything you do with the external mouse is sluggish, until you re-login or restart the machine. I blame a memory leak in the WindowServer for it. Once it has over couple of GB allocated RAM, then the mouse is basically unusable. Especially text selection by mouse is a nightmare :)