This extension Workaround a Bug 469421 - Add a folder column to search results for bookmarks in the library .
Views > Show Columns > check Parent Folder
OPTION: This can display folder hierarchy optionally.
COMPANION: It becomes more convenient when you use "Go Parent Folder " (https://addons.mozilla.org/en-US/firefox/addon/7377
) together with this.
LIMITATION: The parent folder column is not sortable.
FORUM: If you want to ask something about this, please post it to the following forum.http://forums.mozillazine.org/viewtopic.php?t=659689