Where's the Stop/Back button?

of course i have an idea. according to the the Eos Family hotkey pdf document it's both Ctrl Spacebar and Ctrl Alt Q

In MacOsX that would be "Cmd Ctrl Space" in my Nomad

or twice to stop any running timer, and then go to the previous cue

or use Virtual Keyboard, grey arrow left above the green "Play" button

or the red stop sign in case of a running timer and then again, same button other symbol, grey arrow back

good luck!