Oh, never mind... sometimes you DO have to read the directions, duh...

But, for anyone else who doesn't read the directions (Hello, sisters and brothers):

Just click and hold the back button and the little menu drops right down.  ;-)

The arrow to open the tab history of the Back and Forward buttons has been removed in Firefox 4 and later.

Use one of these methods to open the tab history list:

• Right click on the Back or Forward button
• Hold down the left mouse button on the enabled Back or Forward button until the list opens

You can look at this extension:

• Backward Forward History Dropdown: https://addons.mozilla.org/firefox/addon/backforedrop/

Sorry. Doesn't work. Guess I'll quit using Firefox until this is fixed.

That add-on only works if you are using graphic buttons. I use plain text option and the add-on does not have a text "v" arrow in that mode, it just displays a blank space. :-(