How to create a Two Columns Submenu?

If you have a long list of items in one of your WordPress sub-menu dropdowns, you probably want those sub-menu items to be split into 2 columns.

Go to the Appearance > Menus, edit the parent menu item that contains the items you want to display in two columns and in the CSS Classes filed add two-columns-submenu

If the CSS Classes field doesn't appear in the menu options, go to the Screen Options panel in the top right corner and enable it from there.