Thank you @Brathenning for your suggestion.

We should think about ways how to ease your task, but yet providing very general functionality. Joining and splitting measures sounds very special (even MuseScore does not have this function).

What about thinking more of deleting and inserting new measures and providing some graphical way of selecting and copying content (notes, slurs, etc) to a new position? Would that help as well?

Thanks for the answer! I can understand if it's to specific but when you edit pieces changing the measure layout might be necessary, especially if you're editing lute music and maybe contemporary music where equal measure length are uncommen, OMR might also misplace bar lines (btw MuseScore has this function under tools > measures)

The process of copying notes is quite easy in the editor but I can see uses for that. Especially if it manages xml:id which are always a danger when copying elements. Inserting and deletig measures would be great though (if they change the @n of measures dynamically)