Support for multiple scenes
General menu system for switching between scenes.
And also holding state between scenes (i.e. remembering what TwineNode is active when you enter a new scene)
If this is in reference to embedded scenes, then Unity isn't really down with that. A single render pass can only reference a single scene, so two scenes intersecting in a single "parent scene" isn't supported.
This idea with regard to data movement between scenes seems much more difficult and potentially emcourages bad practice (Unity scenes should be generally, wholesale environments, not sharded up).
I'm still into a minimal version of this, but without data sharing.
IIRC data sharing was the point of this request, e.g. if you leave a main mission for a dialogue scene and then want to come back to the main mission and not lose your progress in the main mission.
Putting this here as a possibility to explore in future: https://www.sitepoint.com/saving-data-between-scenes-in-unity/