Scenes are similar to Routines in that they are basically Rules that are only maintained by the mobile apps. However, unlike Routines, Scenes are recognised as separate entities in the developer docs and have their own API endpoint. I suspect that is a historical thing and that ideally they’d be quietly forgotten about outside the mobile apps.
Curiously, there isn’t a way to execute another Rule from a Rule, or at least not one that I know about. If there was I’d drop all my Scenes in seconds for the same reason I barely use Routines.
So is there a way to execute a Scene in Rules? Of course there is as Routines are doing it. Can it be used by the rest of us? Yes. Do I know what it is? Yes. Am I going to tell you what it is? Not in a public thread I’m not as there may be a reason it isn’t documented for public release and I don’t want to do anything to undermine Rules development.