You can set the max-width to none or specify a maximum (400px) with code in userChrome.css in the chrome folder in the Firefox Profile Folder to see more characters.
See http://kb.mozillazine.org/Editing_configuration

Add this code to userChrome.css below the @namespace line.

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */

#bookmarksMenuPopup .bookmark-item { max-width: none !important; }

• ChromEdit Plus: http://webdesigns.ms11.net/chromeditp.html

Hi cor-el,

thanks for you reply. I tried your suggestion, but I did not recognized a huge change. Is 400px really the maximum? For now I'm using a workaround to open "chrome://browser/content/bookmarks/bookmarksPanel.xul" in a new tab, but this is not as comfortable as I wish.

Hi again,

I recognized that the solution from cor-el worked fine for the Bookmark-Menu but not for the bookmark-toolbar.

Does anybody know which item to modify to apply the width to the bookmark-toolbar?

Use the selector #personal-bookmarks:

#personal-bookmarks .bookmark-item,
#bookmarksMenuPopup .bookmark-item { max-width: none !important; }

Hi cor-el

thank you very much for you help. It works fine and now FF really matches my needs!!!