If one goes in Firefox to Bookmarks organise Bookmarks on can see a Folder called Fat Dial.

This is the Root Folder in Fast Dial.

One can with the help of the context Menu place the Root Folder in different places in Bookmarks.

The most common is to make the Fast Dial Folder home.

Please see here

It is also possible to change the name of the Root Folder (called Fast Dial)

To do so go to Bookmarks/Organise Bookmarks/Bookmarks Menu

Select the Fast Dial Folder

At the bottom of the page you will see the name of the folder
Simply change the name and exit

The new name of the Fast Dial Folder (The Root Folder) will now be visible in the Tab when you first open Fast Dial in Firefox

Many thanks