This extension includes a feature for hiding the bookmark name and only showing the Favicon for bookmarks on the Bookmarks Toolbar.
https://addons.mozilla.org/en-US/firefox/addon/multirow-bookmarks-toolbarplus/

Thank you very much.

But when I pressed the "Add to Firefox" button to install, I received the following error message:

"The add-on from addons-mozilla.org could not be installed because it does not match the add-on Firefox expected."

Try:

• Roomy Bookmarks Toolbar: https://addons.mozilla.org/firefox/addon/roomy-bookmarks-toolbar/

I'm not sure if you'll come back to this question but just a reminder that you can abbreviate individual bookmark names on the toolbar right down to nothing leaving only the icon - right click on bookmark>properties>name.

Space is also helped greatly by grouping bookmarks in folders on the toolbar. When you open the folder you can click on individual bookmarks or "Open All in Tabs".

@cor-el,

That's exactly what I want. I instlled it. Thank you.

@alan_r,

Undoubtedly those are great tips. I'm sure many people would prefer that. Thank you, too.

You're welcome

I would use code in userChrome.css to achieve this.

• http://kb.mozillazine.org/userChrome.css
• http://kb.mozillazine.org/Editing_configuration

#personal-bookmarks .toolbarbutton-text {display:none!important}

All you have to do is right-click one of the icons, click "Customize Title Widths," and then click "Icons Only."