I would like to add a number at the beginning of each line. Is there a way to do this?
Depends on how you created them. Separate flows/frames? If not perhaps just Shift-X text.
Jesper
You could also make that a score of 3 instruments, called 1, 2 and 3 and show staff labels.
Maybe even it helps to show the dotted quarter equals 3 eights because then they align vertically too
Good idea. I guess there are many more below, though.
Jesper
One player can have lots of instruments 
Or, hide empty staves.
Indeed.
Jesper
Of course, I forgot the easiest way. 
Jesper