@korner
Are you asking how to do this “outside” XD? Since this forum is about plugin development for XD, this (probably) wouldn’t be the right place for that question.
If you’re asking how to achieve this with a plugin, then the link @gdreyv provided should get you what you’re looking for. The library I mentioned there is just a JS library that can help you serialize the scenegraph (by converting nodes to JSON), but isn’t required.
PS: Please note that if you’re asking about doing this from “outside” XD: Extracting things from an xd file is strongly discouraged due to the frequently changing specs of the file types etc., cf. Is there anyway to extract the files and folder of an XD file?…
PPS: Welcome to the community 
