Support an "open" menu level

It would be nice if the menu.module (which is awesome ... by the way) supported an "open" menu level, if the user navigates to a menu, and click on a submenu item. I'd imagine this would have to be done with either a cookie or session information.

Basically, if you had a main level menu, with sub-menu items, and the main level was opened, then an item in the sub-menus clicked on, the top level main level menu stays open for that menu level. This is the behavior I'd expect, since I'm "navigating" in that menu level - I could then go up, or down to other menu items in the same main level.

For example:

   main menu
      level 1
          level 1 sublevel 1
               item A
               item B
          level 1 sublevel 2
               item A
               item B
          item 1
          item 2
      level 2
          level 2 sublevel 1
               item A
               item B
               item C
          item 1
          item 2
          item 3

In this case if "Level 1" was expanded, then "item 2" clicked on, I'd expect that "Level 1" stay open (expanded).