edit_theme_options - menus option doesn't appear

I would like to grant acces to editors to create/edit or delete menus. If I have set up in functions.php the edit_theme_options capability (above), the editor can access the header and background but not to the "menus".

// get the the role object
$role_object = get_role( 'ch_edit' );

// add $cap capability to this role object
$role_object->add_cap( 'edit_theme_options' );

What have I forgotten?