i have been using the key controller buttons to adjust octaves but when the keyboards split into different sounds they aren't individually adjustable by octave through Mainstage.
when i change octaves every sound on the controller moves.
annoying but maybe a higher quality controller would be more customizable. my hardware synths can do this so i thought for sure Mainstage would have an option.
If you are trying to change the octaves on things within a split patch you best bet would be to select the channel strip that you want to shift in EDIT mode and select the MIDI Input tab. There is a Transpose control there in that page....