If you're happy to try Blender, I did the v3.0 of this series and it was very good (I've forgotten most of it since then though...)
youtube.com/playlist?lis...

Yes, I love Scrivener and use it for all kinds of writing. But it’s not the right tool for branching narrative.

Yes, I’m similar to that: outline the shape of it (I tend to use Onenote) and then work the rest out as I go. Depends on what it is though. If the project is very interactive, I plan a lot more.

That's how you summon an angry Emily Short. 😉
I only know as I've done a lot of work in node graphs, but I barely understand Storylets - I'm hoping to get a chance to use them at some point. (Personally, I find node graphs far easier to grok than linear scripting, and can hit the flow state in them)

Good post, but you're conflating node graphs with Storylets - they're two very different things. You can do Storylets in a node graph, but you can also do them in other systems, and not all node graphs are Storylets.