There are no folders underneath an address book, only mailing lists. So what exactly are you trying to achieve?

Can I change or rename a mailing list?

Double click it.

You can rename any address book this way, apart from the Personal Address Book or Collected Addresses.

These two can be renamed via the config editor, but I'd advise against doing so, unless you are careful to remember you have done this and say so when you ask for help.

Can I add another list?

Since the Address Book starts out with no lists, any "lists" there now were added by the user. Perhaps the terminology is the issue here. Maybe you actually want to add an address book?

In either case you need to see the menu. Both address books and lists are offered under File|New.

I think if you could see the menu you wouldn't be asking this question. So, to see the menu, you can right-click at the top and a pop-up will offer a checkbox you can tick to have it display the menu bar. Or press F10 or hold down the alt key and tap v.

Under View|Toolbars you can, again, select the menu.

One you have sight of the menu bar, File|New|Mailing List will let you add a list to the currently selected address book. File|New|Address Book will let you add another address book.

Note that current designs of Thunderbird show a composite address book named All Address Books. You cannot add new Contacts or Mailing Lists to this book; you must select one of the real address books such as Personal Address Book or Collected Addresses.