I bought a cheap volume knob from Amazon, and by using the generic USB device settings in BetterTouchTool, I was able to remap the left and right dials to various functions on my Mac. I use it for scrolling in my browser and scrubbing in Final Cut. I also have volume control in Spotify. The possibilities are endless. I'll share my presets later.
Now, I wonder: what if I buy a second knob? Will BetterTouchTool recognize it as a separate device so I can assign different functions to each dial? I was considering placing one knob to the left and another to the right of my keyboard. I could then tilt with the left knob and zoom with the right one when using Apple Maps, for example. However, before purchasing the second knob, I would like to know if it will appear as a separate USB device or not (as the hardware will be identical). If it doesn't work I can always send it back. But I thought maybe someone has experience with configuring two identical devices.