I'm developing this app, which I'm currently using for a personal knowledge base, but whose ambitions are quite a bit larger:
https://digraph.app/wiki/topics/39b38b69-1c22-4e98-bb79-661b...
https://blog.digraph.app/2019-07-06-ten-thousands-links.html
This is a new app, although it's an iteration on one that I made more than ten years ago.