I like this add-on, but in order for it to be really useful, it really needs a select all as a top most option. Or a "Delete All" button that applies to everything listed on the page.

The "Find Duplicate" option found hundreds of duplicate bookmarks, but each bookmark has to be selected before being able to delete it.

When running the "Find Broken URL's", it list 8 or more sub sections which you have to select individually to select all in each sub section.

If a "Delete All" button is added, this would make an excellent 5 star add-on.