To add Vertical Divider Lines Between Divi Default Menu Items add this CSS code to Divi > Theme Options > Custom CSS box and click the green "Save Changes" button to save changes:
/* Start Divi add divider to the default menu items*/
#top-menu li:not(:last-child) {
border-right: 1px solid #555555;
margin-bottom: 20px;
}
#et-top-navigation nav > ul > li > a {
padding-bottom: 4px!important;
padding-left: 20px;
}
/* End Divi add divider to the menu items*/
Divi default menu will then have vertical lines added between menu items, like in the below screenshot:
