You can want to config the Brand page as this: https://gecko5.myshopify.com/pages/brands
Please follow these steps below to understand about the way config
You can go to Online Store > Pages > Create a new page & choose the Template is brands
You can go to Navigation > Create a new menu & add the handle is "t4_brands_page"
In Show All link, you MUST set a link is "#*" to make all the menu item display on this tab on the preview
With parent menu like A, B, C, D, E....you can enter link is "#"
With menu item to A (It's the children menu), you can add the link for it as you want.
You can click on "View page" to see the result