Each H9 is actually also a decent MIDI controller. You can use one H9 to send MIDI program change AND MIDI clock to another H9 (or any other MIDI device on your board). So……Here are a few options:
1. You could technically lose the MIDI mouse and just use one H9 to change presets and control tempo on the other H9, but you would also lose a small amount of flexibility in scrolling because you have to press the big knob on the H9 to reverse the preset scrolling direction.
2. I know you don't want any more boxes, but a small MIDI merge box would solve your problem. The MIDI mouse would plug into one H9 and one input of the MIDI merge. The other input of the MIDI merge would receive MIDICLK from the first H9, and the output of the MIDI merge would go to the second H9. This way you would be getting Program Change from the MIDI mouse and MIDICLK from the first H9.
3. Wire up a small single Aux Switch with 2 outputs and plug it into both H9s. You would assign the Aux Switch function to Tap. If you're already using expression pedal in that jack, there is still a way to combine with a single button Aux Switch via a stereo Y-cable.
4. Switch to a MIDI controller that also has MIDICLK, or get something like this:
