There is this very cute/affirming feature in macOS, whenever a keyboard shortcut that is also present in the menus on the menu bar, the menu bar flashes. For instance, you did copy something, the Edit menu flashes, and it tells you that the shortcut was invoked successfully. Would be really nice to see this in Plasma.
It's an interesting idea, but I think it would need support in Qt as the way menus work is deeper than anything we have control over in Plasma or KWin. The one place we could implement this is in our Global Menu widget, which we do have control over. And that would replicate the macOS experience they they also have a global menu.