Edit Flyout Menu module
This Flyout Menu module is created in Journal > Modules > Flyout Menu and can be imported into the header main menu in Journal > Header > Main Menu, in any menu item with Dropdown Type set to Flyout.
The Journal menu system is fully customizable, essentially any mega menu item is a page builder into which you add any modules you want or load a Flyout menu module which is created in Journal > Modules > Flyout Menu.
The Flyout in turn has mega menu items with other layout modules in them, such as Catalog (which displays categories and subcategories), Products modules, Banners, Links Menu, etc.
You can locate what modules are used in each menu from the menu item itself, access Journal > Modules > Flyout Menu > Active Module > Menu Item > ... so in each menu item, you'll see the page builder with rows and columns into which you'll see the modules used. You can change the row and column structure, load different modules, or edit those directly in-place, click on the little Quick Edit button.