Window managers definitely get a first crack at keyboard input. For example, I have a bunch of super-related keyboard combos set in i3wm that always go to it. I

Window managers definitely get a first crack at keyboard input. For example, I have a bunch of super-related keyboard combos set in i3wm that always go to it. I doubt that's the problem you're referring to. More likely it's that the window manager has no consistent means to make any given window/app do anything in particular, like copy or paste. The app decides its own key combos for those. There's no universal way to do it globally short of using nothing but apps that are specifically intended to work with gnome or kde or another uberenvironment's configuration system. Basically, you could bind super-c at the WM level, but you couldn't make it always copy.