For me, I have to travel back in time to the days of DOS and the fantastic outliner Grandview. I don't believe any application developed since then matches Grandview feature for feature, although the new note-apps have other great features. But Grandview introduced me to the power of outlines, and how each node in an outline could be a full-blown word-processing document.

If you're unfamiliar with Grandview, I wrote about it many years ago; in fact, this was my first writing about information management apps:

https://welcometosherwood.wordpress.com/2009/10/10/grandview/

Steve