Looks like the latest version solves some of the problems that previous reviews have complained about. This extension now *is* a manager. Within the extension window you can now move bookmarks, rename bookmarks or open bookmarks. If the search window seems too small you can click the button in the upper right corner, which opens the bookmark manager tab at the current location in your search window. This extension is a good replacement for the "Go Parent Folder" extension that no longer works in newer versions of Firefox.

UPDATE: My one complaint is that when I add a bookmark it is not immediately displayed by this bookmarks manager. Instead I must switch back to Firefox bookmarks to confirm the bookmark was really added where I put it.