DisplayFusion basically intercepts the message that Windows sends to the game that says "you lost the focus" so that the game thinks it's still the focused window.

It should work for full screen games as well, though some are quirky. There are a couple of things you can try for thos:

• Run it from a Trigger rule for the game with a long delay (e.g. 30 or 60 seconds)
• Try opening the game's menu before running the hotkey
• If the games are run from Steam, try opening the Steam overlay (Shift+Tab) before running the hotkey
• Switch to windowed (alt+enter), run the hotkey, switch back to full screen (alt+enter again)

Hope that helps!