The mega menu module lets you create mega menus from existing menus by defining regions and blocks.

The recommended way to add menu items for use with the mega menu module is to add them to a menu through the module_name.links.menu.yml file in a custom module or profile.

Doing it like this will let you commit the menu items to your git repository and will make it much easier to transfer these items between different environments without having to copy database content.

This module is still under development and might have some flaws that still needs to be fixed.