Readit NewsSeems familiar, somehow . . .
There are examples of grouping and some clear hierarchies. But our mental processes are more complex. Things can exist in multiple boxes, boxes can overlap, crosscut, have different priorities, constraints, etc. Conventional hierarchies are too simple.
Of course, that misses the graphical/spatial aspect of other tools, but as josephg points out, these sometimes backfire without a natural, design-encouraged way to organize the content, and a stable frame reference. I for one don't miss the ability to organize my content spatially, even though I do that when working with physical paper. I think that's because of the limitations of the medium — i.e. I spread paper sheets out on a surface, and spread content within those sheets, because it's the only way to group content in a stable manner. The nesting system performs the same function for me in outliners.
Here is a quick screencast: https://imgur.com/a/PXTRgHp
Just a quick note for the inattentive like me: you have to click the "Run" button before executing the `@enter foo(20)` command.
It's the difference between instructions for a user and instructions for a developer, but in coding projects that's not much different.
Sounds like a job for a CONTRIBUTING.md :)