Try the
NoteMapper by CodeFN42. It's Windows-only, so any Mac users seeing this shouldn't get excited. It inserts into an instrument track, and you need to send the output as you would send MIDI to any MIDI-friendly device. I don't know of how to do this in Studio One without using something like loopMIDI, where you can treat loopMIDI's output like a controller that the Pro EQ3 recognizes. So the basic idea might be something like this:
Instrument Track - Keyboard input, NoteMapper output, input monitor on
Instrument Track 2 - Notemapper input, loopMIDI output (you'll need to create this as a new external instrument)
Use loopMIDI as your external controller'
I haven't figured out yet how to control a Pro EQ3 filter stage with this process but I'm sure it's doable. I'll give it a shot when I have more time. Hopefully you can figure out a recipe and share it.
Be forewarned that NoteMapper requires you to enter a parameter type (e.g., note or controller) for
every note you want to use. You'll want to save this as a preset!