Hugh wrote:

... Is a relatively new digital tool that describes itself as "a story
development and writing app", a "story sequencer" and an "outliner and
writing app". Clearly designed for scriptwriters and novelists, its main
display combines three panes: a timeline that has some hierarchical
functionality, a "story logic" pane that is slightly reminiscent of
flowchart apps such as Flying Logic, and a writing pane.

It also has several other features that are likely to be particularly
attractive to fiction-writers in the Hollywood tradition - for example a
way of associating "set-ups" and "pay-offs". But I mention the
application also because I remember that some members of this forum
engaged in composing non-fiction have in the past made good use of tools
for fiction, and it may be that some can make use of this.

Causality is paid for on a subscription scheme, and it's available for
both Windows and macOS. Its developers have big ambitions. I can't vouch
for it being bug-free, but so far I've found that the app has been put
together in a serious and professional way. It's also worth mentioning
that as an app it's noticeably colourful - Technicolor-colourful, some
might say!

Details at https://www.hollywoodcamerawork.com/causality.html

I saw this mentioned on the Scrivener forum a couple of days ago and downloaded the free version to see what was what. I'm working on a large non-fiction text in the history of medicine, and have been using Tinderbox and Aeon timeline to keep all of the factual, conceptual, historical details relatively manageable, but the whole narrative structure has been problematic so I was open to new ideas, and after just a few hours of playing with it, Causality does seem to offer some goodies.

It basically gives an overall graphic outline of synopses, and the main writing will still be done in Scrivener, but the graphical presentation is very flexible and really does help to clarify things. The Sub-Arcs which allow 'unpublished' trajectories and repositories of themes is - none of which appear on the graphical outline until they are added - are a great idea: e.g. brainstorm a few digressive points and then distribute through the main narrative at a later date.

I'd jump immediately for the full version if there was a way of linking from the synopses to e.g. Scrivener document links, but at the moment I'm still exploring.

Of course it can be used as a more simply outliner too: I used it this morning to outline a lecture for next month and and the clear graphics seemed to offer a very effective way of working.

I'll see how it goes over the week-end