Structured metadata is actually a planned feature, which I guess I need to prioritize now 
It is also how we are planning to implement manual sorting. The original plan wasn’t necessarily to expose such metadata directly to users, but I can see how it makes sense to be able to edit and add whatever you want to the meta.
That being said, we probably won’t be implementing it as part of the markdown content in the form of frontmatter, as we are moving away from raw markdown as the underlying storage format.