I created attachments to be used on the plain ValueTree:
So if you use these attachments on the public accessible AudioProcessorValueTreeState::state, then it gets stored together with the rest of the state…
Maybe that helps…
It seems that “isAutomatable()” is only a hint for the host, that is not controllable, if it gets exposed to the user… It is covered in that thread: How can i set a certain parameter not Automatable?