The Divi theme lets you select from various header menu formats, including a slide-in menu. Normally the slide-in menu will have only the top level links displaying, with all submenus closed. If instead want the slide-in menu to start with the submenu of the current...
slide-in menu
Styling the Divi Slide-in Menu
The Divi theme includes several header menu layouts, including a slide-in menu. The slide-in menu is a bit of a mash-up of the top header, main menu and mobile menu, so while Divi Booster doesn't have a specific section of slide-in menu settings (yet), some of its...
Make Slide-in Menu Top Level Items into Links
The Divi theme's Slide-In Menu displays menu links in a vertical bar which is revealed when you click the menu button. When opened, it displays a list of top level (parent) menu items. Normally, clicking on one of these menu items takes you to the linked page....