Im a biot confused by this as well because I think I've only ever set my volume pedal once and it seems to work on everything - its not locked so I assume it works plug and play/default but you can override per rig? Is that what you mean by "could" vary?
I've never messed with it as it just works so only curious...
.... hmmmm - I need to improve my "explaination-skills"
My actual understanding is, that having the volume pedal settings locked in performance-mode (... which applies the same settngs for all rigs in performance-mode) BUT NOT in browser mode (... rigs come with their "own" settings) it just hqappened - depending on the rig that I choose in browser-mode), that "the sound was gone".
I guess my problem occured after minutes or hours, depending on the rig that I did select in browser-mode (... and the settings that came with the rig).
I hope the above is more helpful, than confusing ....