I/O View
In the Edit window, I/O view provides Input and Output selectors on audio, Auxiliary Input, Master Fader (output only), MIDI, and Instrument tracks (corresponding to the controls of the same name in the Mix window).
Edit window I/O view (audio track)

Channel strips in the Mix window always display Input and Output selectors as well as volume and pan values, so there is no I/O view display option for the Mix window.