How embarrassing - a whole new grid UI theme for the WD TV Live that doesn’t allow you to add anything to the grid!
No way to “favourite” a service, no way to access a plugged-in drive (except through predefined favourites that were added using the Mochi theme…).
PS: If you press the red button or select that option (“select content source”) in the UI theme choice menu in the setup, it barfs and says “Date” until you reboot the box).
Old Mochi theme still works just fine! Please don’t take that away!