Great nifty tool. Very fast and accurate.
Need to understand the options once we run the Bookmarks DUPES.
Options to mark the duplicates in many ways.
For a huge volume of bookmark duplicates use one of the intuitive 'marking' options.
(Example in each duplicate group, select all but latest).
We can also manually choose and remove but when faced with a huge volume better to leverage the tool.
It also creates a "Dupes' folder we can move (similar to Recycle Bin on a computer) before permanently removing or choose to directly remove. As the Add-on warns, once removed there is no way to get back. But that is how it works. (It is like when we empty recycle bin)

Awesome tool. Kudos to the creator (s)