Sorry I let this slip for a couple of days, Dave. I made a mental note to look up the manual again and break it down, but then I forgot.
It looks like a volume pedal lets you sweep between two different delay configurations, but an external tap switch can do quite a few things for you. Here's the list from the manual:
1. Toggle between configurations.
2. Control the bright button.
3. Control the tap-div button.
4. Toggle the mod button.
It looks like only one of those features can be controlled at a time, though.