>> I was thinking mostly about lists which are good as writing prompts – themes, dramatic situations, tropes, kinks, etc. <<

I have some that I originally wrote for a different bingo fest, that aren't going to be used immediately. And I can make new ones too.

>> (Though, I realized at some point while making this that it could be used as a kind of "Unfuck your Habitat" motivational tool <<

For that I recommend Goal-Fish:
http://www.goal-fish.org/

>>...you know, I hadn't thought of coding it to allow for multiple categories, but I bet I could figure out how.<<

I hope that works out.