My new favorite Keyboard Maestro shortcut allows me to toggle between audio outputs (Built In Output device and my USB output). The Built in volume controls my iMac speakers, the USB output controls my Amp. So, combined with the superb Rogue Amoeba’s SoundSource, I can easily bounce back and forth between controlling my music volume (Roon, Spotify, archive.org) and my Zoom volume using my keyboards volume controls. This sounds like it would be easy and it is, sort of, by using switchaudiosource-osx (available as brew install switchaudio-osx from command line). 

Anyway, this is a huge problem solver for me. Stoked. Click pic below for larger version if you want to see the actions.