Spiney speaks with great wisdom. Here’s some more tidbits about that stuff:
Additive scene loading is one possible solution:
https://discussions.unity.com/t/820920/2
https://discussions.unity.com/t/820920/4
https://discussions.unity.com/t/824447/2
A multi-scene loader thingy:
My typical Scene Loader:
Other notes on additive scene loading:
https://discussions.unity.com/t/805654/2
Timing of scene loading:
https://discussions.unity.com/t/813922/2
Also, if something exists only in one scene, DO NOT MAKE A PREFAB out of it. It’s a waste of time and needlessly splits your work between two files, the prefab and the scene, leading to many possible errors and edge cases.
Two similar examples of checking if everything is ready to go: