Header Menu with muli-level sub menus

[Kris40]

I am trying to figure out how to configure the header menu widget so that it has two sub levels, like a cascading drop-down menu. For example I have 10 links, 5 of which fall under a sub category. I want to display the first 5 links under the main heading, then the next 5 links under a sub-heading.

For example:
MainHeader
  -- Link1
  -- Link2
  -- Sub-header
        -- Link3
        -- Link4
  -- Link5
  -- Link6
  -- Sub-header
       -- Link7
       -- Link8

[Umang Jain]

Hi Kris, thanks for the solution, but it is expanding drop down horizontally, can you please tell how we can achieve it for vertical drop down.