Magit has a sub-package called Transient (also made by Jonas Bernoulli) which is what powers its UI. It's absolutely brilliant for making porcelains.

I'll have to take a look at that, I love magit's UI for its ease of discovery. Before magit I didn't know that 'git bisect' existed, nor how useful it was.

I can think of a few other utilities that would really benefit from a similar interface. Certain use cases of org-mode come to mind. There's nearly always a way to do what I want in org, but sometimes it's a pain to figure out even simple use cases without going to the docs or a forum. It's just something that seems to go hand in hand with all really powerful tools.

I may play around with writing a custom mode for my particular workflow of using org for literate programming. There are a bunch of commands I find useful, but don't use often enough to have committed to memory. I'd also love to be able to pull up a pop-up buffer, like magit's commit messages, whenever I want to edit a source block in more detail.