Picture in Picture Mode Window won't stay on top

I would like to use the Chromium/Chrome Browsers Picture in Picture feature as Overlay in my Game.
But it wont stay on top of the Game window. If i pin a xfce window to stay on top
it doesn’t work either.

Is there a Setting that overrides the games i run in lutris to stay always on top?
Or hat someone an idea why this feature does not work?