archretro - how to come back to the webapp/Steam UI during game play

I have successfully configured some retro ROMs @ WebApp and I was also successful in launching them and playing them.

The official method is to press the "xbox button" located at the center of the screen. But it seems that for NES games, this doesn't do anything.

So my question is: is it possible to fall back to the UI while playing a NES game and only having controllers as available input method?