About lightmap loading

Since Unity has saved the lightmap data into *.unity file,this is a scene file. when you load lightmap,then you need to load the scene. while SceneManager.LoadScene only works when the scene is added in build setting dialog or editor mode code.
if I have lots of scenes and I need to add the scene to the scene list in build-setting menu. this is not very convienient. Especially when we build the scene objects into assetbundle and load then in runtime.
i dont know why unity do such things that save lightmap data into unity scene file. is there any special consideration?
Anyway how to solve the problem?

any help will be appreciated

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