As a former Opera user, Firefox's bookmark manager always seemed like its weak spot to me.
Luckily I found "Sidebar Bookmarks Search Plus" (https://addons.mozilla.org/en-US/firefox/addon/sidebar-bookmarks-search-plus/) and it has been a must-have addon for me for a long time. When searching my sidebar bookmarks, it shows an extra pane under search results with the exact location (tree) of any found item.
Unfortunately its author has recently deleted it and, given the amount of categorized bookmarks I have and how often I use the search function, I really need an alternative.
If anybody knows of an addon that I can replace its functionality, please let me know. Thanks in advance.