I'm not aware of anybody actively working on documenting this better/at all. It's relatively little used; admittedly, possibly because it's mostly undocumented.

We're always happy to have people work on the docs. We've generally been using the wiki for documentation like this, and if you're interested in helping, I can point you places (or rather, I can ask some awesome folks to step in and help point you, since they are awesome and know the current taxonomy etc).