This exact functionality is not provided by WebEasy. Such menus can be created using JavaScript and added to WebEasy sites using the Custom Script Assistant. One place to look for scripts would be on the following page:

Alternately, there's a Menu object in the "Objects\Objects - Advanced" folder which is similar but you have to click on it to make the menu appear, rather than just roll over it. When you add this object to the page a dialog should appear where you can specify what menu items to show.