Hi mike,
Indeed it seems Ableton has not implemented that feature. I just didn't know that was a possibility, since it seems like a basic thing to have
There is not much in the way of VST3 documentation in the manual, but I did find something regarding AU presets in this article
https://help.ableton.com/hc/en-us/articles/209775145-AU-preset-handling-in-Live-9
, which is very suggestive to the way the guys at Ableton want you to interact with plug-in presets.
The suggested solution seems to be to access the presets first in the plug-in UI and then save them as a Ableton presets. This works for VST3---the saved presets are named *.vstpreset and can be handled/automated in the usual way.
It is a bit cumbersome of course, because one has to save presets twice (in S-Gear and in Ableton) to keep things synchronized, but it works.
Thanks for the help to you and kierank both!
Orfeo