Thanks for everyone’s help.  To follow up: I got it working by mapping the Preset (A in my case) to Hotswitch 5 to the function I wanted to twiddle (Slow/fast/brake).  Then separately mapping Hotswitch 5 to a midi CC (#21 in my case).

Note that I appear to be able to map hotswitches 1 and 4 to Program, 2 and 5 to Slot A, and Hot Switches 3 and 6 to slot B.  In my case, I almost always have a modulation or Fancy pants delay in Slot A, so I’m fine with this limitation.  It’d be ice to be able to map just “Preset MyFooModulator always maps onto Hotswitch X” but I can see why this would also be problematic when combining presets without a control mapping strategy.

From there, the magic for fast/slow/stop appears to be that a single CC #21 – Value 0 toggles the state between Fast and Slow. A single CC #21 – Value 127 activates the brake.  This relationship also holds on most of the modulation algos. I’m stil workign on my morningstar controller to try to get the right toggle behavior, sometimes my slow/fast labels end up out of sync with the H90. I might need to simplify.

For Delays, the perform setting I am interested in is the Repeat, which appears to be similar CC# – Value 0 turns it Off, CC#21 – value 127 turns it On.

With the hotswitch mappings, the behavior I’m getting is I’m able to override the MIDI using the actual footswitch assuming I’m on the correct page of the hotswitches (which is accessible by tapping the perform knob live).