Hello,
Sorry for the delay and thank you for your patience.
We do not have the option to move the menu to another column, and it is not possible to customize with CSS.
Please check the option on how you can create a mega menu: https://xtemos.com/docs-topic/create-mega-menu/ and add it to the site: https://xtemos.com/docs-topic/adding-menu-to-the-site/
As for the another issue. Our default drop-downs in menu are implemtend by common practice applied in all the theme, including Storefront: “position: absolute”.
Custom CSS cannot change the behavior and nature the drop-down menu. You can set full-width, Set size or Sticky menu in the menu items.
You would better re-arrange five level menu into mega-menu blocks by means of titles and times if different size and style.
If you have any questions please feel free to contact us.
Best Regards