Changing a Submenu to a Mega-menu with Beaver Builder

• Step 1: make sure you turn on the CSS Classes in Screen Options when viewing your WordPress Menus
• Step 2: for the parent menu item (for the submenus you want to be mega-menu) add "mega-menu" as the CSS Class (no quotes) In this example the Parent Menu Item is "Categories"
• Step 3: Save your Menu
• Step 4 if you want the mega-menu to be full width, then add the following CSS and tweak as necessary:

UL.fl-menu-horizontal LI.mega-menu > UL.sub-menu:after
{
 content: "";
 display: block;
 position: absolute;
 left: 50%;
 top: -1px;
 height: 101%;
 width: 100vw;
 transform: translateX(-50%);
 z-index: -1;
 box-sizing: border-box;
 border-top: 1px solid #efefef; 
 background-color: #efefef;
 /* This is for full width shadow.
 You need to turn off "sub-menu drop shadow" in the menu module.
 Remove this if not needed. */
 -moz-box-shadow: -2px 4px 9px 0 rgba(134, 134, 134, 0.451);
 -webkit-box-shadow: -2px 4px 9px 0 rgba(134, 134, 134, 0.451);
 box-shadow: -2px 4px 9px 0 rgba(134, 134, 134, 0.451); 
}