Tfthacker started a thread on Twitter where he lists all the outliners he’s used starting with MORE.
The first one was a program editor I did on Unix for C programmers in 1977. I started with the source for a Unix line-oriented editor called YALOE and added dive and surface commands (left and right square brackets) for navigating the hierarchy, and commands to restructure the outline. I’m not sure this app even had a name. It had a language parser built in, so it could take bits of code and turn it into an outline structure.
When I showed the app to some of my friends who were not programmers, one of them asked if they could use it, which set me off in a different direction, an outliner that had nothing to do with programming. The result was High Files, which also had a simple tabular database. Outlines could