A single Reality Composer Pro project can have multiple scenes. A scene is an entity hierarchy stored in the project as a .usda file that you can load and display in a RealityView. You can use Reality Composer’s scenes to build an entire RealityKit scene, or to store reusable entity hierarchies that you can use as building block for composing scenes at runtime — the approach Diorama uses. You can add as many different scenes to your project as you need by selecting File > New > Scene, or pressing ⌘N...