I’m adding some more info on top of the above today - hopefully useful! I think this will be revealing.
I exported an old instrument of mine, which uses only the default (polling) guiMode and a similar principle of chnset sliders with buttons.
In VST everything (except Live hiding automation lanes) seems to work as intended! Sliders move by chnset without Csound gestures enabled. This plugin was the final iteration after we struggled with the old “chnset_gestures” (What happened to CHNSET_GESTURES?). And now I know why I “abandoned” AU. Because VST worked and AU not, which is still the case in the default guiMode. AU doesn’t record automation on sliders, only on momentary buttons. To make things more confusing, I couldn’t get automation recorded also on radio-grouped buttons. Consequently, chnset changes also don’t get recorded.
So chnset has seen some sparks of light in VST and in default guiMode but not in AU. While in the queue mode, AU seems to behave better. The “gestures business” works in VST and default mode without actually using it - witch seem ideal, but in the queue mode, it seems to work partially for AU. There seems to be remnants of the old ghosts lying around combined with the polling/queue mode dualism and a layer of Ableton’s caprices on top. The sticky tapes start to make development very difficult for me - I don’t know in which corner of the game I shall be manoeuvring.