In the way the Chrome browser manages bookmarks, this does it the same way. They are all within a single page, in a hierarchy that allows a drill out to a right-pane showing sub folders or to the URLs within the folders. This is a very easy and elegant way to manage bookmarks and I have been hoping either Mozilla or an extension would provide it. It also serves as a way to access all your bookmarks so you can hide the book mark toolbar and gain some vertical space: just pin the Book Mark Manager tab. I gave it 4 stars because it does not appear to support drag-drop of a URL from the address bar which is the only way I create new bookmarks and a feature supported in Chrome.
Response to developer's response- I don't see 5 stars on the right of the address bar but do see see three dots which list a variety of options. One option is to bookmark the page but there is no ability to control where it is saved in your book mark folders.