Mega Menu

To activate the mega menu, you should go to Appearance > Menus > Open your primary menu > Toggle a menu item > Open the "Menu Options"

Enable: Turn on the option to activate the mega menu.
Sub-Menu Alignment: Choose an option for the sub-menu alignment.
Sub-Menu Width: when you choose sub-menu alignment (Left, Right, Center) you will see this option to set the sub-menu width. If you choose Full or Container, this option is not available.

After enabling the Mega menu, you can see all the sub-menu displays in one column.

To separate them into different columns, please click on the window icon to open a list of grid layouts, you can choose a prebuilt layout or make a custom layout.

Then you'll see a popup including all the possible prebuilt grid layouts, you can choose one of the available or create a custom layout.

Choose a grid layout and start adding new elements by clicking on the "+" icon in each column. You will see a popup including all the available elements to choose from.

Click on an element you want to add to the column. Then drag & drop elements among columns to fit your need.

You can drag and drop elements from 1 column to another column and reorder them easily.