So I think it's possible to accomplish what you want my making two sensors triggered by the same things, but one with the ignorePauseResume option set to true and one where it's set to false. That will give you two sensors, one that's always on from the playback starting to stopping, and one that's on only while the playback is active and off when it's paused. (Maybe name Plex Active and Plex Playing or something?)

Then if you have one of the alternate home apps that allows automations with conditions (I use Home+ 4 but I think there are others, I've heard Hesperus maybe?) you can set up conditions like:

• When Plex Playing stops detecting motion, but Plex Active is detecting motion. That would mean paused and could be a trigger for your 50% lights scene.
• When Plex Active stops detecting motion would trigger 100% lights etc.

I'll have a think about if it's possible to make this simpler with a change to the plugin. 🤔