Use this Add-on cautiously
Today, 11/5/20179, I tried Deduplicator for the first time using FF56. Unfortunately it removed Bookmarks that I did not consider duplicates. Because of the way I save and organize Bookmarks there may be no solution since I provide my own Bookmarks' name in properties. Some are located elsewhere. I had THOUSANDS of bookmarks, so I should have deleted the Bookmark duplicates individually. At this point I don't know if deleting individually is an option. So this is more an advisory for those who are trying this like me for the first time.
I use FEBE (by Chuck Baker), which I recommend so this issue can be overcome to return to a previous Bookmarks backup.
I'll re-rate this once I get more experience using it, If I'm able to get it to work on the thousands of Bookmarks I do consider to be duplicates they will have to be handled manually. This will require that the Parent Folder be identified.
I'll be looking for a way to isolate those I do not want deleted within my system of organization and just let the Deduplicator work without doing it manually. That actually is a requirement in my case due to the large number of duplicates.