Expression map triggering a different channel

I looked and did not find this, so please point me in the right direction if it’s out there.

How do I control an instrument (in this case a physical pipe organ controlled by a midi controller) with expression maps and key switches where the key switch is on a different channel than the notes?

Ideally, I’d like to be able to play and record the instrument in Dorico.

I can simulate the instrument using Organ Assist (it works like an external VST controlled by midi).

The stops on each of two manuals and the pedals (each on their own midi channel) are controlled by key switches on a different channel (same channel for all of these).

Unfortunately at the moment you can’t send key switches via an expression map on a different channel.

One possible workaround would be to add an extra instrument to your project that is assigned to the same plug-in but a different channel, and insert the required key switches on that instrument as real notes, then exclude that staff from the full score layout so that you don’t see it in the printed score.

That sounds like it would work. I’ll try it.

Ideally, I’d like to have some visual indicators on the score when organ stops change, but it wouldn’t be the end of the world if they aren’t displayed.

I’m primarily using this to record an organist (or sequence music) and playback via computer when the organist is not available. - if it goes into the other organ assist software easily, mission accomplished.