The Add Bookmarks dialog windows is not really the best example of usability in Firefox. The default window just shows a ‘Create in Bookmarks’ folder and the user has to click the down arrow to expand this menu and display his folder structure. If you like your things organized you probably have created a rather large folder structure in which you place your bookmarks.
Most users do not place them in the folder Bookmarks. A little CSS tweak expands that Add Bookmarks window to display most of your folder structure without having to press any buttons. To apply this tweak you need to find the file userChrome.css and open it in a text editor.
Add the following code at the end of the file. You might want to change the height that is set to 40 to another value depending on your monitor resolution and folder structure.
@-moz-document url(“chrome://browser/content/bookmarks/addBookmark2.xul”) {
#addBookmarkDialog {
min-height: 40em !important; /* Adjust this value to change the default height */
}
#folder-tree {
visibility: visible !important;
}
#keywordRow {
display: -moz-grid-line !important;
}
button[dlgtype="extra2"] {
display: -moz-box !important;
}
#expander, #keywordRow + row {
display: none !important;
}
}
Before:

After:

via [userstyles]
Related posts:
- Save Firefox Bookmark Searches
- Firefox Bookmark Sorting Extension SortPlaces
- Help Firefox is not showing the File Download dialog anymore
- Change your bookmarks toolbar appearance in firefox
- Firefox Bookmarks Toolbar Tweak
- Firefox Auto Bookmark
- Bookmark Emails In Thunderbird
- Display Firefox Unsorted Bookmarks More Visibly

Maybe you can use OpenBook extension for Firefox. At https://addons.mozilla.org/it/firefox/addon/42
Bye ^_^
VinS – Like your post of the OpenBook extension – it’s a beautiful thing.