WP Menus inside another menu plugin

Hey everybody!

I am looking for any WP plugin that adds an option to choose another existing menu while creating new menu, so that way I should have menu within another menu. I need to divide my large menu into smaller sub menus, and looking for some easy ways to do that.

Example:

I have following menus - sub menu 1,2 .... 9

- I should be able to create main menu (20 items)
    1 name,  source - link
      1.1 name1,  source - sub menu1 (20 items)
      1.2 name2,  source - sub menu2 (20 items)
      1.3 name3,  source - sub menu3 (20 items)
      1.4 name4,  source - sub menu4 (20 items)
      1.5 name5,  source - sub menu5 (20 items)
      1.6 name6,  source - sub menu6 (20 items)
      1.7 name7,  source - sub menu7 (20 items)
      1.8 name8,  source - sub menu8 (20 items)
      1.9 name9,  source - sub menu9 (20 items)
    2 Blogs
    3 Pages
      3.1 Pages ....
      3.10 Pages ....

Thanks in advance.