I would like to share the results of experimenting with the changing of the speed of the trill to obtain other symbol patterns like the following ones:
I have changed the default symbol for “trill wiggle” (all speeds) to Bravura character: U+E210 (stem). Now I can get different stem patterns that increase or decrease the separation between the stems. The stem pattern is obtained creating a trill and hiding “tr” symbol. The fanned beams are created independently, hiding the notes and stems of all notes under the beam except the first and last one.
The advantage of doing this, is that the distance between stems is kept independently of the music spacing and it is also kept in parts (I tried to obtain similar results with bravura text, but then I had to adjust the end of the text in parts which is very time consuming if this notation is used a lot).
This can also be obtained with the wavy glissando line. In that case, you can also change the inclination of the pattern, but you can’t change its separation.
It would be nice that a future implementation of lines could include this kind of pattern repetition, allowing a change of speed, like in trills. Just a suggestion.
PD: Of course, doing this will not allow to use the usual wavy trill or glissando line…