It's rather common for Firefox extensions to want to let the user trigger an action. The way to do that is the menu bar. With the default menus in the menu bar, the tools menu is usually the only choice that makes any sense, so most all the extensions seem to stuff their commands inside the tools menu. Pretty quick, with the default and all the additional items, that menu is way too big to deal with.
This simple extension just takes all "new" tools menu items, and moves them into a new "More Tools" menu. New items means, items that it can find being put in, after it starts watching. Almost any item added by an extension falls into this category.