What LukeLanFaust explained is the way to go. There will not be a built-in system for that because there is absolutely no concept of active scene in the engine. Sup.appendScene(...) will create some actors and stuff from a data structure. Sup.loadScene(...) do the same, except it will destroy all current actors first.
But once a scene is loaded (or appended), you can create or destroy anything you want. That's why an active scene doesn't make very much sense.
I hope that's clear enough :)