Yes, it’ll work as a MIDI controller but there are limitations. The H9 will output a single PC message on one channel when a preset is changed. All of your downstream MIDI devices will have to be set for the same channel and you may have to fiddle around with your presets to make everything work. Any ‘mid stream’ pedals will also have to support MIDI Thru:
H9 —> pedal x —> pedal y —> pedal z
Pedal x and y have to be able to pass the input MIDI signal thru to the MIDI output connector. If not, you’ll need a MIDI splitter.
I think H9 can be set to output a CC message that corresponds to the expression pedal but I haven’t personally tried that. I have set one up to output CC messages using aux switches and that works great.