I'm trying to customize my hybrid category navigation by adding some external links. I've inserted the following code into the functions.php file with no change to my site. I thought I'd used this code before and it worked. Not sure what's going on now.
add_filter( 'hybrid_category_menu', 'custom_cat_nav' );
function custom_cat_nav( $menu ) {
$menu = false;
$menu = '<ul id="cat-nav" class="menu sf-menu">';
$menu .= '<li><a href="http://somelink.com">Some link</a></li>';
$menu .= wp_list_categories( array( 'depth' => 4, 'exclude' => '1', 'title_li' => false, 'echo' => 0 ) );
$menu .= '</ul>';
return $menu;
}