I pin the same article to six boards over a few weeks with different graphics. Every few months I lose track and queue an identical image+destination pair twice, which is the one thing everybody says not to do.
What I want is dumb and local: hash the image (perceptual, not md5 - I resave PNGs constantly) plus the normalized destination URL, and flag it at queue time. Not a block, just a "you already pinned this to Home Decor on Aug 3" line. Does any tool do this already?