Welcome to the community @Arcus. 
I believe the documentation still needs to be written. The application itself is not actually done yet (see this topic if you are interested in following along with the development), so I think the primary focus thus far has been focusing on that.
If anyone has experience writing documentation and would like to contribute to drafting a Rani Wiki, I’m sure that would be appreciated! Notes on how to contribute to the project are in the README on the GitLab page: