From the Dashboard Hover over Divi and Click on Theme Customerizer
Click on Menus
From this page, you can click on an item, hold the button and then move the mouse around to drag it to a different spot.
1. When you click the down arrow next to custom link, you will find options to customize it.
2. You can add a url that someone is directed to when they click on the title item for the menu. You can also change the category name.
3. Remember to click the save & publish button at the top after making changes.
Learn More about Mega Menus
Here’s an example of a Mega Menu.