Serious question: I enabled a Plasma option to make windows transparent when I hover over their corresponding 'application rectangle' (sorry, not sure what to c

Serious question: I enabled a Plasma option to make windows transparent when I hover over their corresponding 'application rectangle' (sorry, not sure what to call it) in the panel. It drives me mad but I just can't figure out how I everenabled it. Ditto with transparent menus. Can anyone advise? In general I'm very happy with Plasma but it does expose UI options that can really harm the experience.