One of the more frustrating things that I’ve found in any notation software is the Glissando Playback in the harp. The harp oftentimes may use distinct pedaling, etc. to have a variety of different combinations that lie outside the key. As a result, any playback that just follows the key will always be limited. In Sibelius there is Zawalich Plug-In that allows you to generate the midi messages for unique scales, but it can be a tedious workaround and I still always wished there was some way of natively editing the glissando playback itself.
So in short, have glissando playback options to:
-diatonic (white notes only)
-customize scale (as if manipulating the pedals of the harp)