You have Get's but you need Set's, you just need some way to set the key and scale ??
reaper.MIDIEditor_GetSetting_int(editor, 'scale_root')
reaper.MIDIEditor_GetSetting_str(editor, 'scale', '')
reaper.MIDI_GetScale(MediaItem_Take take, number root, number scale, string name)
reaper.MIDI_SetScale( take,
9,
"102034050607",
"User Reascale")
or
reaper.MIDI_SetScale( take,
9,
2741,
"User Reascale")