Actually I am working on an app which should include many features of Tiddlywiki. It’s called “Next Notes”:
I rethought the “Ownnotes” app and wanted to create a “notes” app, which gives you much of what a Tiddlywiki gives you: Sharing, Tagging, Search, WYSIWYG editor in well-known Markdown style (and maybe more). Everything should integrate in nextcloud as good as possible. But personally I am not a fan of storing notes in files, like it is handled in Tiddlywiki. Because I think the files in my nextcloud should be separated from the notes or (wiki) articles I write, the app stores them in the DB at the moment.
I would suggest to work together, if you are interested in this. (Actually I would appreciate contributions and help with the sharing backend).