Workflowy (https://workflowy.com) is the most interesting outliner-type app I’ve come across in a while. I wish it weren’t a web app, and wonder if it could be “reinterpreted” as an Emacs mode or something. But it’s really good, and really interesting. I also like they way they’ve integrated kanban boards—great way to manage projects in a really lightweight way.
These are the kinds of tools I wish there were more of. I always felt like the old Mac world was full of slightly undercooked but cool apps for organizing information, and no other platform that I know of has really come close to that kind of exploratory spirit.