If you were working with WordPress customizations, than I am sure you have used the add_menu_page function of WordPress. It adds a New Menu Item in the admin navigation. I used it for many times, but I saw that when I use it with one sub menu, it automatically adds main menu as first submenu. I was working with Reports section in one of project where I need to generate 3 reports. I adds main menu as Reports and I need to add 3 submenu under it.