Right now the “Developer Portal” which is linked from the main menu of steemit.com is the central place for documentation. It is a work in progress though.
You can also join the SteemDevs discord group where community developers go to chat: https://discord.gg/B29Bbng
Yeah, the developer portal is a bit lacking in substance. It provides very basic examples to get you started, which is good, but as soon as you want to look at some of the more advanced functions, there is a lot of guesswork involved...
And now it seems all those APIs just got replaced....
Thanks for the links though. The people in this community are its saving grace.