This icon may move between bars. If you display the Bookmarks Toolbar, it may be on the right end. When you close that toolbar, it may move to the Navigation Toolbar. It's a little confusing. For your style of working, where do you want it to appear?

I appreciate your reply.

I have both the Navigation Toolbar and the Bookmarks Toolbar displayed. The bookmark icon appears on neither, unless I also open the Customize Toolbar window (by right clicking a blank spot near the tabs and choosing Customize...). When the Customize Toolbar window is open, the icon appears to the right of the Home button (a good location for it). When I press Done, the window closes and the bookmark icon disappears.

Try this extension from Alice0775:

• bug582139 (Allow full customize bookmarks button): https://addons.mozilla.org/firefox/addon/bug582139/

Thanks for the link to the fix! This is exactly what I needed. Thanks, again.

You're welcome

Just btw., it's always there (in both cases) so you probably must've customized something; screenshot attached, Firefox 7.0a1 x64

@Corliya

You have the Menu bar hidden and have the orange Firefox menu button visible.
That icon on the Bookmarks Toolbar will disappear if you unhide the Menu bar which has the Bookmarks menu.