I am using empty noteheads witht he “3 spaces as a notehead”-trick.
By default, the accents on these are pretty inconsistent, but even after adjusting them manually, when reopening a project, they randomly jump around again.
Here’s what I achieved with manual spacing in a violin part some days ago (I know it’s not perfect engraving, but it was consistent):
so you can see, the issue appears to be random. Sadly, I noticed it after I sent a badly engraved score (which I thought I took care of) to my musicians…
I’ve (finally) been looking into this. The problem is that the approach of using space characters as noteheads for “headless” notes really can’t work reliably. In order to resolve the positions of the articulations, accidentals, etc., Dorico relies on the bounding shape of the noteheads, but for a space character, there is no bounding shape: just a width. The apparently random behaviour is happening because of tiny variations in the calculations of the bounding shape.
You would probably have better luck using an empty graphic scaled to roughly the right size for a notehead.
Obviously in the longer term what is really needed is either a native way to handle this kind of glissando notation, or to hide a notehead (or perhaps both).