I'm about to build a large site with a vertical menu in the left sidebar. I know I can do this with a plugin and custom menus, but then each page would have to be added individually. Can the Atahualpa menus be displayed vertically and used in the sidebar? Or is there an easier solution?

Just use the custom menu widget in the sidebar without using the WordPress menu.

So it defaults to a page menu.Very cool, thanks. I started trying to style it using the widget options and the page menu options. Neither seemed to work so I'm guessing I have to use the css inserts.

Yes... CSS or using perhaps a menu plugin that has the styling you want.