My shareware program reads abc, imports lyrics from text files to add to the tune, can print up to 6 staves together out of a total of 16, uses 32nd notes and grace notes, and can write to MIDI and abc.(It can also write Songwright files.)
Scoring is not its main aim, but the output MIDI files could be input to a specialist program.
So why isn't anyone using it? Registration encourages further development.
I am currently planning an entirely new facility, 'note profiles' which will allow most MIDI effects to be applied to any single note, and edited graphically.
This could be used, for example, to pan one note from left to right, ramp up the volume, and so on. This would provide the flexibility associated with sequencers in a more user-friendly way (I hope!).