Alexander Deliyannis wrote:

I use SENSE quite regularly; it is my tool of choice for long and
complex texts.

It is the only editor I know that can display a full hierarchy in its
left pane, right down to the paragraph level (one line per paragraph). I
can switch from overview to detail seamlessly. It is a two-pane outliner
which can be used as one-pane too: the tree navigator can be hidden and
full control of level expand/collapse etc. is available in the text pane
via keyboard shortcuts.

In addition, the Viewpoints feature effectively turns it into a
'relational' text editor, much like Brainstorm, as you can be working on
various parts of the same document in separate windows while still
maintaining another with the overview.

Thanks for that, Alexander. The above features do sound interesting. Who would you say the main competitors are here? MS Word? Scrivener? I'm intrigued by Sense, but somehow I haven't managed to figure out where I'd fit it in within my various writing processes.