If you're still sporting both the old Microsoft Edge, and also have the different channels of the new Microsoft Edge browser installed, you might have experienced some issues with syncing your favorites. Well, your pains have been resolved. As spotted by our friend Richard Hay, the latest Microsoft Edge Dev release now has an option to remove duplicate favorites.
— Richard Hay (@WinObs) January 24, 2020
Although we haven't seen the feature on our end yet, it has been confirmed by Microsoft as new. As expected, it appears as though the remove duplicate options can be accessed from the Favorites menu within Edge Dev.
Richard Hay also reports that it "works like a charm." The feature appears to be a stopgap for a full resolution of Edge's various sync issues, as it removes duplicates, but doesn't stop them from occurring in the first place. In a blog post from Wednesday, Microsoft notes that "Favorites sync issues, including sync not working, deleted favorites reappearing, and favorites being duplicated" are still in the plans for a January release. The company also mentions some other features planned for this month, including sync of browsing history between devices, sync of installed browser extensions between devices, and the option to set a custom photo as the New Tab Page background photo.