In addition to other ideas relating to organization and discoverability, I’d like to suggest that documentation would be firmly in sync with reality, and every feature ideally mentioned along with the version(s) of scala it appeared in.
The only document I recall which mentioned specific versions is Wildcard Arguments in Types, and yet I think either the versions evolved with time (if the current state is accurate), or they were describing a plan at some point but one which didn’t pan out and wasn’t updated.
Here’s another example: this document Macros Spec describes “quoted identifiers” as something that is part of the language, just like quoted blocks just below. And yet no known version of scala supports these, instead continuing to complain about “symbol literals”.
If the documentation is at odds with reality, people might learn not to rely on it, making it not as useful.