It seems like markdown YAML frontmatter or some sort of metadata is being talked about. I’d propose a plugin to allow users to reorder notes based on an index stored in the metadata, whatever it ends up being.
I would use this to set up the structure of books generated directly in Obsidian.
An easy version might just be to use the metadata in the obsidian file list. Hardmode might be allowing reordering via drag and drop in the file
I feel like this should have been suggested before, but I haven’t been able to find a similar suggestion yet.