Sorry there was a cut and paste error in my first post
I'm probably not the first person to discover this. I couldn't find anything similar in the archive though so……...
If you have a contour shuttle then you have a hardware fader that can control a selected cues master volume.
In Qlab Create 2 OSC cues with Hotkeys
Increase Master Volume
/cue/selected/level/0/0/+ 1
ctrl-V
Decrease Master Volume
/cue/selected/level/0/0/- 1
shft ctrl-V
In Contour Shuttle Settings…..
Turn Jog Left Type Key: Control+Option+v
Turn Jog Right Type Key: Control+v
Enjoy!