Hello Sean, welcome to Feng Office Forums!
In that case you may find interesting the Development section of the forum, but regarding documentation, other than that in the wiki and the one in the forum.. I am afraid we do not have much. We are aware this is not good, but that is why we always welcome anyone willing to contribute with this, translations, new features, etc.
Either way, soon with the new version it will be way easier!
Best regards,
Francisco