Continuing the discussion from Opportunities for non-coders to contribute:
Thought I'd start a new topic for forum-specific mentoring, advice, etc.
Unfortunately with Discourse there is no compendium or book of knowledge. However, I have to give a huge recommendation to keeping a close eye (daily or weekly at least) in https://meta.discourse.org/ if you want to track the latest changes and best practices:
Their "howto" category at https://meta.discourse.org/c/howto is particularly a good resource and is probably the closest thing to a tutorial.
Their Support & Feature categories particularly are useful to understand how to do "X" (and also when "X" isn't possible!).