For this, we use Pandoc's YAML metadata blocks or approaches inspired by it. Our data publishing package MiniDocs (which is a prerequisite of TiddlyWikiPharo), provides a YAML metadata importer/transformer to native Pharo dictionaries that can be added to tiddlers. An alternative route from tiddlers metadata to Markdown could be easily implemented (but, as told our focus has been Markdown to WikiText migrations so far)