• Press the Shift key while an entry in the drop down list is highlighted to disable "Switch to Tab" and see the URL.
• Use the cursor Right key to select an item marked as Switch to Tab in the drop down list and copy the URL to the location bar.
• Open the URL in a new tab by using Alt + Enter on the highlighted entry.
• Open the URL in the current tab by using Shift + Enter on the highlighted entry.

Are these four steps in a procedure, or are they four different ways to accomplish the goal? I've never used the versions of Firefox since that feature was implemented so I can't visualize doing any of them either way.

Is there some way to disable the Switch To Tab in the configuration file? Does the about:config access still exist?

The Switch To Tab "feature" is the primary reason that I have declined to Switch To "Rapid-Bug-Development" Firefox and plan to remain with Firefox 3.6 indefinitely.

Whichever person(s) decided to implement this "feature" obviously did not have a clue as to the usefulness of opening a tab which is identical to an existing tab while, for example, investigating a labyrinth of data sheets on a technical website. After it is opened, browsing continues on the new tab, which makes it easy to return to the page from which one departed without hitting the Back key umpteen times and waiting while the pages are re-displayed in reverse order (among other less efficient alternatives). The "user" just returns to the tab for the page-of-departure to resume, regardless of whether s/he also wants to close the tab on which s/he continued browsing.

If you try to open the same URL in more than one tab then you may have the "Switch to Tab" feature preventing that.

• Press the Shift key while an entry in the drop down list is highlighted to disable "Switch to Tab" and see the URL.
• Use the cursor Right key to select an item marked as Switch to Tab in the drop down list and copy the URL to the location bar.
• Open the URL in a new tab by using Alt + Enter on the highlighted entry.
• Open the URL in the current tab by using Shift + Enter on the highlighted entry.

In response to Blacklisted's comments, cor-el lists four different was to do the same thing.

Dislike of this feature is not a good reason to indefinitely stay on an old version (and unsafe) version of Firefox, a better option is to disable it to meet your own preferences. For instructions see https://support.mozilla.org/en-US/questions/798155