What is the "Scene Injection Map" and where is it documented?

It’s an optional feature that’s rarely used.

There is already a default map so there is nothing extra you need to do.

The default mapping is

this.sys.add     → this.add
this.sys.cameras → this.cameras
this.sys.load    → this.load

etc. In that example, a custom mapping is given:

this.sys.add  → this.makeStuff
this.sys.load → this.loader

Because cameras is absent, there is no this.cameras property, just as the docs say.

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