Firefox (56.02 64bit) is saving duplicate bookmarks. Example: 1. I go to specific web page on a specific web site. 2. I forget that I have already bookmarked it - and in a specific folder. 3. Not knowing I have it bookmarked already, I ask Firefox to bookmark that page and ask it to do that in the same specific folder it is already bookmarked in. 4. Firefox ignores that that page is already bookmarked in that specific bookmark folder and (a) does not say "Edit this bookmark" but instead (b) goes to the area where you make a new bookmark, and (c) even though I say to bookmark it in the very same folder that page is already bookmarked in, Firefox just saves a duplicate bookmark there. I have (a) backed up the bookmarks as an exported html file and then closed Firefox; (b) deleted all the "places files" in the Firefox Preferences default folder; (c) deleted all the bookmarks json files and saved only the exported backup bookmarks html file in the bookmarks folder; and then (d) restarted Firefox. Those efforts changed nothing in Firefox behavior. It continues to bookmark pages that are already bookmarked instead noting there are preexisting duplicates and just asking instead if you want to edit the already existing bookmark. What do I have to do? Delete Firefox from my computer completely and then tell a brand new Firefox installation to import a saved html bookmark backup file? First I thought the problem was Firefox Sync, so I disconnected, cancelled the Sync account, and made a new Sync account but did not connect to it. Didn't help. My copy of Firefox acts as if it does not want to really "manage" my bookmarks. Can you have too many? Is there such a thing as too big a bookmarks file? Can you help?