Manage bookmarks using DuckduckGo browser

[eto12]

I'm using DuckuckGo browser and have 3 "Imported " categories inside the "Bookmarks" main folder. that are all basically the same thing (with a few exceptions) and have all the same sub-folders(categories) ! How do I merge the categories?

Using Firefox browser there is a "Manage Bookmarks" choice, where I can open sub-folders and transfer/merge like sub folders, not so using DuckduckGo ?

thanks in advance