Tested on same Win10 machine with latest Samplitude ProX6 build 21610 :
- with SL 8.0.10 plugin state is saved properly, I can make an edit like erase frequencies and just save Samplitude session without rendering the plugin. Next time I open the session SL shows the edit in ARA plugin.
- with SL 8.0.20 plugin state is not saved anymore. Strange things is Reaper saves plugin state with 8.0.20.
I think the bug comes from this new build from Spectralayers.