Oops, there seems to be a "nesting" problem with the sections in that article because that third section doesn't appear until you expand the second one.

If you do not wish to use the Refresh feature to address toolbar corruption, you could try the following (you might not need the second one):

(1) "Restore Defaults" button in the Customize tab (appears toward the bottom center).

Please see: Customize Firefox controls, buttons and toolbars.

(2) Rename the file(s) that store toolbar and window layout information.

To do that, first, open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Show Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then rename xulstore.json to something like xulstore.old. If you see a file named localstore.rdf, rename that one to localstore.old.

Start Firefox back up again. You will need to re-enable the menu bar from the toolbar list as described in the first section of the article.

I submitted an edit I think will fix the problem of the third section nesting in the second one, but it will need to be reviewed by someone who has a better understanding of how those wiki pages work.