We have recently added the ability to copy paste entities from one scene to a scene that belongs to a different project. Before we only allowed copy pasting between scenes of the same project.
When you copy paste entities that have asset references to a new project, we will try and auto-match those asset references to assets in the new project based on the path of each asset. So if for example you copy paste an entity with a model component that references a model asset, then if a model asset exists at the same path and with the same name in the new project, the pasted entity will match that.
This should be a useful feature if you are used to forking your project and making changes there and you want to bring back changes in the entity hierarchy to your original project.