Linear / proportional note spacing

Workaround:

1. Add another instrument (ex: Tambourine) // as "Meter"
2. Fill it with the smallest notes you want to use as a basis. (e.g: 16th.)
3. In same staff: Right click on the beam of any group of notes (you have just filled in) and apply: "Select > All similar elements in same staff" option.
4. Open inspector and tick on the "Local relayout" box. (It prevents the interaction of the tuplets with the Meter.)
5. Open mixer and mute This "Meter" instrument.

a sample score is attached.

This feature is necessary not only for your usage case, but for much contemporary music where, instead of traditional measure and figures with submultiples of a beat, a purely analog or proportional time notation is used. The bars, usually indicated as broken lines, or short marks crossing the upper line of the staff, represent a beat of the indicated metronome value. The duration of notes is proportional to the length of a single beam and the note attack timing within a beat is proportional to the notated distance from the preceding metronome mark. See for instance Berio's Sequenza I for flute (1958):
https://www.youtube.com/watch?v=htVoNBH-5RY
https://www.stretta-music.com/es/berio-sequenza-nr-389913.html
https://es.laphil.com/about/watch-and-listen/luciano-berios-sequenza-i
See also p 152-153 from
http://ufdcimages.uflib.ufl.edu/UF/00/09/80/70/00001/notationperforma00…