1) Create a Custom Menu.
2) Under the ‘Link’ menu option to the left, add a name (Link Text) for your Parent menu label.
3) Add a hashtag (#) as the URL, like this:
4) Drag and drop your custom link to the desired position in your Custom Menu and ‘save’.
*NOTE – in some browsers this parent link will reload to the homepage. Currently there is no easy way within WordPress Custom Menus to completely remove a link for a parent menu item.