Athens does this with [[bidirectional links]] and ((block references)) that let you to take notes on anything from any page. Just [[link]] or ((reference)) another page or block - and voilà! - you can now go to this page and see all the places that linked back to it. The next time you press [[
or ((
, you will be indexing through your previous notes, helping you connect the dots. You've starting creating a graph of your knowledge!