The Drupal Kit’s header area displays the main menu’s first and second levels (L1 and L2). To show deeper levels, place “Menu blocks” on individual pages or groups of pages as shown below.
There are two ways to place menu blocks on pages. To place a menu block in the layout of the general-purpose Flex Page, use Layout Builder. To assign a menu to display in a region of the site on multiple pages, use the Block layout page