How to create a menu child of an other menu? How can I create a menu child of an other menu. 
Drupal menu are links to pages or an other content type.
I want a main menu that can expand sub menus by clicking on a menu item.
So, there is a module that can create menu children of a menu?
You can use the Menu block module


  .. allows you to display blocks of menu links starting with any desired level of a menu and limited to any desired depth.
  
  .. you can choose to expand all menu links with children or to root
  the menu tree to a specific menu item.