That's the thing. There's nothing really "custom" here. The files themselves are all still standard markdown with yaml frontmatter. The only difference is that there's now a nice, performant interface for getting an overview for all those files - something that you could fairly trivially make with a script, if you really needed to recreate it. And the file specifying what your views were is, itself, plaintext. There's no lock-in here, and the spec is open and well-documented.