In CC 2019 there is now an option in the Edit Menu to Consolidate Duplicates. I've been waiting for this feature for years. I often import sequences from other projects that I don't control, and I'm left with a mess of duplicated clips pointing to the same media. Thanks for adding this, Adobe!
But...it doesn't seem to work consistently and there's no documentation that I can find on the feature. Sometime the duplicate clips disappear. Other times they stick around when they shouldn't. There's no dialogue or log that I can find that tells you what happened when you clicked that magic menu item, so it's hard to figure out where it went wrong.