pretty sure this isn’t unique to KDE/Plasma - i think i experienced this with all Linux DE’s that i’ve tried
in MS Windows, if a window has focus and you click in another window, the click is always passed to the unfocused window
with KDE/Plasma this is not always the case regardless of how one sets the “Inactive Inner Window Actions” option - for example, if you have a context menu open in a focused window, it takes 2 clicks to activate and pass the click to the inactive window: 1 to dismiss the context menu and the other to raise/focus the inactive window
this is a long standing annoyance i’ve had with all Linux OSs and i’m wondering if there’s a solution