Overlay That Overlays Everything at the touch of using a shortcut

I was thinking it would be cool to have an overlay that overlays everything and displays Discord like an overlay does with transparent settings and that jazz.

like, a layer over the screen so you could passively use Discord whilst doing your thing on Google Chrome, playing a game, watching something. 

Overlay that overlays Discord over everything. The Very frontest layer and brought to the surface by using the Overlay shortcut. Just a thought.