Currently, we know of two different methods of including one scene in another.
The first method is the simplest, and is generally what would be used when adding one scene into another.
For a scene that already exists in the game files, the scene file can be edited in a text editor, and a REFERENCE node can be added as a child of some other node in the scene. This child node will need to have some transform, and a SCENEPATH node in the list of ATTACHMENTS. This is the only attachment that this node type may have.
It should be noted that this method will cause the reference scene to inherit some properties of the parent scene. So for example, if you reference something to the space station scene, the object will extend the region within which you cannot warp, so it is not an appropriate method for spawning objects relative to a space station scene.
The second method is more advanced, but seems to get around the problems with the first method.
This method utilises the SELECTABLEOBJECTSTABLE in METADATA/SIMULATION/<some other folder...>/ as well as the GcObjectPlacementComponentData struct in an entity file attached to the model.