In one of the topic BUILDING MULTIPLE LEVELS/SCENES
One Ready Leader Said
Hello @Ziadjbt78 ! No, that way which you use will not work in the Unity. At the moment there is a development of a new multi-level system, but it is not yet ready, when it is available, it’s hard to say. With it, you can export your multi-level projects to the Unity.
its the last line that is confusing I Can’t Export it to unity3d