I'm using this extension for the sole purpose of restoring the behavior of older versions of Firefox to save bookmarks in the Booksmarks Menu by default instead of Other Bookmarks like newer versions of Firefox do. This extension works well for that purpose and has a few other features (which I don't use).

On a side note, it's insane that Firefox doesn't default to saving bookmarks in the Bookmarks Menu (or even better, allow you to set the default folder for bookmarks) and requires an extension to fix this.