Interesting, thanks. It does sound like there's a lot to build on there so I'll be interested in seeing where it goes. Some of my best "productivity" memories are with the "free" copy of OmniOutliner that came on my first Macs, and I think you have the bones to bring that to the 2020s.
https://support.hogbaysoftware.com/t/how-does-bike-relate-to...
I think core summary is:
1. Wanted to control own text editor. Building off NSTextView was limiting 2. Wanted to use structured document format. Plain text was limiting