Not nearly as hacker-y as this, but I'll plug Reflect here. Probably my favorite tool for this so far. Best continually-improving UX, but there's a subscription cost. I happily pay it.
Do you have a link?
Mindmaps are trees. Maybe you're looking for concept mapping software like cmaptools?
This isn't a real Buzan-style mindmap, though, because the words aren't on the lines.