When using X (or Xwayland), programs can request the `clickthrough` attribute. This lets mouse-clicks and focusing go through the window as if it weren't there, which is useful for overlays which the user does not want to interfere with the actual application behind - for example integrating `glava` into a desktop. Currently in Kwin this does not seem to be possible.
https://wayland.app/protocols/wayland#wl_surface:request:set_input_region