[brazen1]

I suppose that is pertinent!  Sorry.  I'll update the post so it's clear.

Media Center PC = Microsoft XBMC
Microsoft MCE Keyboard = Keyboard
Microsoft Windows Media Center SE = PC

I use alt + F4 to close all players as you can see in the 1st picture.
On a side note, I map F6 to open KODI as part of the KODI activity.  The way I do this is:
Right click KODI in your W10 menu and select 'More' and then 'Open file location'.
Right click KODI and select properties.
Highlight the 'shortcut key' and press the F6 button on your keyboard and then save it.
Now you have a shortcut key to open KODI by pressing F6.
You can also assign that new shortcut key to your KODI activity using the 'Keyboard' device I referred to above where your new F6 command will be sent in the startup sequence along with turning on all your other devices like your display and AVR so that everything involved is one simple button press on your remote.
Be aware, most 'F' keys are already in use by Windows.  F5 and F6 have no ill affects when using them as hotkeys.  All other 'F' keys are bound by Windows and I don't suggest they be used for anything except their original intensions.