Harp glissando and runs in MIDI editor.

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.