David Alfonso has done a great job and put together a repository that helps you with the export of tiddlers. All you need is to export all your tiddlers bundled as one single HTML and then follow the instructions in the README.
TiddlyWikiPharo is capable of similar exportation and we start from the single HTML TW file that we can de/recompose almost at will, because we can manipulate the tiddlers inside a data narrative. As shown in the malleable systems wiki example, we're mostly focused in conversions from Markdown to WikiText (TW's format) as it is our most felt necessity, but migrations from WikiText to Markdown are in the radar, combining/extending TiddlyWikiPharo with Pandoc (future needs/funding will tell if/when is implemented).