Well here's an image from Helix Edit. Sorry I couldn't make it any bigger/clearer. I've added the volume block to a footswitch to copy PJ-Bassist's example. I've had a play around and dipping the pedal simply results in engaging the volume 100%, it effectively controls the bypass, like an on/off volume function. Unfortunately using Edit has not shed any light on the matter and I'm all out of ideas.
It's odd, and quite disappointing as I've found the bulk of the unit incredibly intuitive, one you get the hang of it. This however has me stumped.