In the Key Edit page an “instrument column” would be useful. This would list instruments used in the entire project, a section of it, or a user-defined selection. The column could be quite thin and instruments could be recognised by their colour tabs and abbreviations.
This would allow orchestration on the fly. The user could easily change the assignment of instruments to midi notes in the Key Edit page with instruments that are currently not included in the Key Edit page. The need to switch to the Project page to select a new instrument would be minimised. It would reduce workflow from having to continually switch pages. The user could spend more productive time in the Key Edit page rather than having to continually switch pages between Key Edit and Project views.