The problem with focus-follows-mouse on macOS is the top menu bar. If you had it, and tried to mouse to the menu, the menu would switch out from under you. I

The problem with focus-follows-mouse on macOS is the top menu bar. If you had it, and tried to mouse to the menu, the menu would switch out from under you. I have some notes in a file somewhere about how a Mac-native focus-follows-mouse could even work, because I want it. It would end up being a rather different implementation than the X Windows style.