I guess I found a bug.
If you set Sticky Menu Effect: Fade then Mobile Only and Desktop Only options are both acting as Both.
If I set “Sticky Menu: Mobile Only” and “Sticky Menu Effect: Fade” then the menu is appearing even on desktop.
If I set “Sticky Menu: Desktop Only” and “Sticky Menu Effect: Fade” then the menu is appearing even on mobile.
GeneratePress – Version: 1.3.16
GP Premium – Version 1.2.72
Other 3rd party plugins were deactivated during the test.