I've been thinking about how to transition to markdown on and off for the better part of 7 or 8 years, and the possibility of opening my workflow up to "coding" agents has given me the push to actually finalize my work.
Lexicon is a plain-text format for legal contracts, built on standard Markdown. You write contracts using normal Markdown syntax with a few conventions — YAML front matter for parties and metadata, numbered lists for clause hierarchy, bold text for defined terms, anchor links for cross-references. The source file is valid Markdown that should render cleanly in GitHub, Obsidian, or whatever.
When you need production output, it can be compiled to .docx (or PDF/HTML/etc) with automatic clause numbering (1, 1.1, (a), (i)), cross-reference resolution, defined term validation, cover pages, signature blocks and schedules.
You can play with it here: https://play.lexicon.esq. If you want to compile to docx, you can use the tool here: https://github.com/RichEsq/lexicon-docx