Support for YAML is probably a long way off but it could go several ways:
- Hardly Nothing: Just strip YAML headers in document previews (just like Marked)
- Minimal: Implement syntax highlighting for YAML headers along with stripping YAML in document previews
- Nice: Implement basic metadata (say title, date, and author) per-sheet and per-group, in an "internal" Ulysses format, and optional inclusion of this metadata as YAML when exporting to Markdown. Plus #1 and #2 for use in external files.
- Really nice: In addition to #3, allow users to define their own custom fields. To preserve some simplicity, these need only support strings of text and could be the same for all projects.