It’s not absent or obscure, it’s at the bottom under “lists”.

Also the front page rank is the determined by the number of upvotes divided by time to a low power, times a flagging factor. It’s open sourced.

That's the basic algorithm, but there are quite a few additional factors- see https://news.ycombinator.com/newsfaq.html.

That document could use a clarification for the "Ask HN or Show HN" section. I didn't see an option to make an "Ask HN or Show HN" in the UI. Do we just add that text manually? Does the software recognize it as special keywords? If so, is it case-sensitive and does it need spaces or a colon?

Ask HN is just for text posts (submissions with no URLs). That's stated there.

Show HN is explained in the rules that are linked to from the FAQ: https://news.ycombinator.com/showhn.html

... so it seems like all the information is present? Admittedly in a somewhat cryptic form.