I already have Design Extender and it has been installed.
**UPDATE** I just removed and re-installed Design Extender from a fresh download and it still have no way to edit menus.
**UPDATE 2** I GOT IT WORKING. Turns out you need to make sure you turn on "Scripts" in your "Invisible Elements" panel within "Preferences". I will chalk this issue up as "User Error".
I hope this can help someone else.