Here’s a preset I just built which should do what you’re after:
Oriental_Keyboard.mhp (1.9 KB)
The octave C7 - B7 notes (assuming Midi Note 60 is C4) should be used as toggles for quarter tone lower pitch for the matching key.
The preset dispatches the below octaves to 12 channels, based on the note name.
Pitch Bends in MIDI apply to the entire channel at once, your synth must be listening to notes on all channels (‘omni mode’ should be turned on, or at least the synth should be listening to channels 1 - 12)
If you’re using the same synth that’s producing sound to play the notes, you should turn off the ‘local control’ setting.
Different synths may have a different pitch bend depth, in that case, the Transform pipe which is bypassed in the screenshot should be adjusted accordingly to match the desired tone pitch.
The octave range and the octave to control the toggles could be increased.
Let me know how it works. 