I do not think we have very much about the engine DB or how to access it at all, in the official documentation, because it's usually considered a bug if users have to manually fiddle with that. And if you write your own script to connect to the engine db and do stuff there, and it's broken in some next upgrade, that's considered to be your own problem.

We do have lots of official documentation about the DWH database, because accessing it directly (read-only!) is an official API (including compatibility views per version, etc.).