A one-stop shop for all the technical GCA docs.
The GCA Data File Reference Guide (2022) is here. This now includes the contents of the previous guide and the Updated Data File info, in one handy PDF. Could probably use some cleaning up and whatnot, but at least now everything should be in one place.
The Plugin Reference Guide is here. This is incomplete and very much a work-in-progress, and progress is slow.
Also, if you’re writing a plugin, see this post.
And here’s a post explaining how to update GCA itself to the newest release version.