This mega-menu is a page. You can add what you want on it : Blocks, layouts styles on blocks, ..
A page-type is installed with Anitya, let you create mega-menu in one click, the second one is to publish them!
Welcome to new Anitya I'm John,
This custom template is the traditional system of drop-down menu with the ability to display mega-menu or multi-child columns, icons, search-bar... It consists only of CSS so a very fast execution, with no script.