[oldpoem]

Hmm i guess i'm missing something. No matter if i enable or disable use exclusive mode in dsplayer settings the option 'use a fullscreen window rather than true fullscreen' is always greyed out.

The settings display mode shows full screen with 1080p but the option 'use a fullscreen window rather than true fullscreen' is greyed out. I click alt+enter and kodi goes to window mode and the option 'use a fullscreen window rather than true fullscreen' is greyed out. This is correct.

I click alt+enter again kodi switch to full screen the option display mode shows full screen but the option 'use a fullscreen window rather than true fullscreen' is still greyed out.
I tried to reset settings to default but nothing happens. The option 'use a fullscreen window rather than true fullscreen' is always greyed out. Independently from the option use exclusive mode is dsplayer settings.

What i'm missing?

edit
Maybe i found something. If the selected renderer is madVR and try to reset the settings the option 'use a fullscreen window rather than true fullscreen' is still greyed out and i can't switch the fullscreen mode.
If i select as renderer EVR now and reset the option 'use a fullscreen window rather than true fullscreen' is now selectable and i'm able to change the fullscreen mode.
Now i go back to madVR as renderer and the option is stuck again.

The reason why i ask. If i'm in real fullscreen and try to play a movie with dsplayer the kodi gui never disappears and i get no movie picture. In the background i can hear the movie sound. No matter if i use exclusive mode or not.
I have to switch to use a fullscreen window in kodi and now i'm getting a movie picture with dsplayer. I could stay forever in fullscreen window mode but sometimes i have bad picture tearing and i need the true fullscreen.

As aracnoz said with MadVR it take control of fullscreen device (exlusive mode or not). So Kodi will always in window mode that's probably why that option always grayout.

In my system I have to set MadVR in exclusive mode for it to works normally. Disable exclusive mode makes it not smooth and lot of tearing.