We want this developed as a widget/plugin - no customization of WP code or theme code.
This will be similar to accordian menu like moo collapsing categories, except that rather than displaying categories and subcategories, it will allow the admin to place links and text for the links, to appear (appear where, for example, the top-level categories would appear in moo collapsing categories, and other links to appear where subcategories would appear in moo collapsing categories)
The purpose is that we have an external website with product categories and subcategories, and we want to make these appear in a collapsible accordian type sidebar menu.
To see moo collapsing categories in action, as an example of what this menu will look like when finished:
See: [url removed, login to view] and see the menu on the left sidebar.
The theme we are using is Suffusion.