Given the Windows Server 2012 charms disconnecting from a server seems difficult outside full screen. Win + C is required to disconnect from the UI.
Can one assign a special key to real-time delegate recipient of windows commands - or must that depend on the application full screen?
For Windows key combinations it's a setting under Local Resources. By default they are sent to the remote computer only when using the full screen.
For session commands in an RDP session Ctrl-Alt-End brings up the same menu as Ctrl-Alt-Delete.
For those who want to set it in an rdp file:
https://technet.microsoft.com/en-us/library/ff393668(v=ws.10).aspx
Determines how Windows key combinations are applied when you are connected to a remote computer.