There are various statistics that would be nice to have quick access to. The top two for me would be range/highest note/lowest note (both written and sounding), and active frames (a non empty measure). These would ideally apply to either a selection, entire flow, or entire project.
Range stats would be great for arranging purposes.
Counting active frames is often done as a lot of copyists/engravers charge per frame instead of an hourly rate or a page rate. Counting frames in a large score manually is quite tedious.
Of course there’s more stats that could be useful, but these are the two that come to mind.