[themodelplumber]

I wonder if an extensible editor (example: Atom) could do both of those things with Markdown files. Assuming by styling you mean things like being able to highlight and custom-style some text, even in a typically text-only view of a markdown file. It wouldn't be a big surprise if that could be done...somehow. Collapsible points ought to be doable for sure.

Personally I use other methods for styling within markdown, for example emoji, tags, link formatting with brackets (for things that are not really links), etc.

I also take any list that's longer than 8-10 items and break it up by category or reorganize it so it's less visually overwhelming.

Otherwise you may find it helpful to look into more rich-editor-style notetaking solutions like cherrytree or Notecase Pro. The latter is proprietary but I used it for years and was very happy with it. Good luck in your search.

https://www.giuspen.com/cherrytree/

https://www.notecasepro.com/