Allow more fine grained control over MIDI mapping

[brettrp]

Your idea

• Allow more fine grained control over MIDI commands mapped to actions. In particular, some buttons (and also pedals) can send down (127) and up (0) messages separately. Allow control over how these are mapped
  -- e.g. ignore up message, toggle off on up

• Allow mapping of more actions to buttons - e.g.
  -- entry of rests
  -- slur mode
  -- enharmonic spelling changes
  -- or potentially anything that you can map a keyboard shortcut to (using Preferences - Shortcuts)

• Allow sets of MIDI mappings to be saved (useful if you're switching between different MIDI controllers)

Problem to be solved

Allow long passages to be entered entirely with a MIDI keyboard, minimising the need to go back to the computer keyboard.

Prior art

No response

Additional context

See this issue:
#17549
and this discussion:
https://musescore.org/en/comment/1190275

for some limitations encountered using the current mapping feature.

[bkunda]

I'm pleased to say we are already working on a major design that should address this issue.