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SurveyJS
Open-Source JSON Form Builder to Create Dynamic Forms Right in Your App. With SurveyJS form UI libraries, you can build and style forms in a fully-integrated drag & drop form builder, render them in your JS app, and store form submission data in any backend, inc. PHP, ASP.NET Core, and Node.js.
You might try twine? It's mostly used for making interactive stories but being able to link and move things around is helpful for organizing and plot fiddling. Especially since you've be able to set up and then move between plot points fairly easily as well as re order them since twine lets you see connecting threads between sections.
So there's a piece of opensource, free software similar to Scrivener called Manuskript. It has some excellent world-building and plotting tools. I've enjoyed it so far.