ld_dashboard_add_nav_menu

gistfile1.txt

function ld_dashboard_add_nav_menu( $menu_items ) {
    $menu_items['all']['hello-world'] = array(
        'url'   => get_the_permalink() . '?tab=hello-world',
        'icon'  => '<img src="https://via.placeholder.com/24" alt="Hello World Icon">',
        'label' => 'Hello World',
    );
    return $menu_items;
}
add_filter( 'learndash_dashboard_nav_menu', 'ld_dashboard_add_nav_menu', 10, 1 );

function ld_dashboard_after_content_callback() {
    if ( isset( $_GET['tab'] ) && 'hello-world' === $_GET['tab'] ) {
        echo '<h2>Hello, World!</h2>';
    }
}
add_action( 'ld_dashboard_after_content', 'ld_dashboard_after_content_callback' );