Hi, you should simply place something similar like:
[From MIDI A] -> [Filter out all but Channel 1] -> [Dispatcher using ch1, 2 and 3] -> [To Virtual A]
[From Virtual A] -> [Remap channel 1 to whatever first synth is listening to] -> [To MIDI A]
[From Virtual A] -> [Remap channel 2 to whatever second synth is listening to] -> [To MIDI B]
[From Virtual A] -> [Remap channel 3 to whatever third synth is listening to] -> [To MIDI C]
[From MIDI A] -> [Filter out all but Channel 2] -> … -> [To Virtual B or something else]
…
Assuming Keystep37 out is connected to MIDI IN A.
You could daisy chain the mono synths with THRU ports if they have them, then you could send all to MIDI OUT A on Midihub, and configure the synths to listen to channels 1, 2, 3, as needed.
That’d be the general idea, let me know if you have any questions. 