Is there any effective way of writing these in the Midi editor?
What I want is to quickly write harp glissandos lasting X beats / bars, in Y scale, from note A to note B.
For runs, I would like to be able at least to easily switch between 4/5/6/7/8 notes per beat.
Is there any hidden option I’m missing on the line tool? 
Any suggestions?
I use step input for this and then “massage” the data afterwards.Particularly velocity.
Probably a 32nd note quantise, I can’t remember.
What I found helpful was reading about how the pedals work when you engage them. This creates unison or doubled notes in the glissando.
This can help to get a more authentic sound.
I didn’t find it that difficult to get my head around but I did read a great article that explained it well but I can’t remember where I read it.