It makes writing configs less tedious using templates.

Not really sure what you mean by "documents" though.

Some config formats like Yaml or Jsonl support multiple "documents" per file

I mean multiple files.

> But weirdly given its focus on schemas I couldn't find any way for a document to link to a schema in-band!

In cue there's no real distinction between "schemas" and "documents". If you say:

   value: string
   value: "abc"

then cue "unifies" the definitions for `value`, sees that "abc" is a string, and therefore `value` is valid.

Yes I know, but there's no in-band way to say "this file conforms to the schema in this other file" like you can with XML or JSON schemas.

For Cue you would probably just want to #include a file... but as far as I know you can't do that.

That makes it far less useful for IDEs, linters and so on.

I don't think there's any reason they couldn't add that feature. Just a bit odd that they haven't already.