And there's some additional information in the very brief user manual on MIDI mapping other than the PC mapping, and a Zoom interface explorer at https://www.waveformer.net/zoom-explorer/. This could be handy for anyone who wants to build a controller to allow all six effects to be switched on and off without scrolling.
For the original MS pedals (MS-70CDR, MS-50G), mapping of MIDI CCs to effect parameters only works smoothly for the first three effect slots. For the remaining three effect slots, changing the effect parameters will trigger a patch reload, which will result in audio being muted for a brief moment.
For the MS+ pedals (MS-70CDR+, MS-60B+, MS-50G+) the MIDI CC mapping works for all effect slots.
CC Target
2 Effect 1 on/off
3-14 Effect 1 parameter 1-12
17 Effect 2 on/off
18-29 Effect 2 parameter 1-12
33 Effect 3 on/off
34-45 Effect 3 parameter 1-12
48 Effect 4 on/off
49-60 Effect 4 parameter 1-12
63 Effect 5 on/off
64-75 Effect 5 parameter 1-12
78 Effect 6 on/off
79-90 Effect 6 parameter 1-12