Create List of Child Pages

function wpb_list_child_pages() {

    global $post;

    // Only get child pages of the current page

    $args = array(

        'post_type'      => 'page',

        'posts_per_page' => -1,  // get all child pages

        'post_parent'    => $post->ID,

        'orderby'        => 'menu_order',

        'order'          => 'ASC'

    );

    $child_pages = new WP_Query($args);

    $output = '';

    if ($child_pages->have_posts()) {

        while ($child_pages->have_posts()) {

            $child_pages->the_post();

            $link = get_permalink();

            $title = get_the_title();

            $excerpt = get_the_excerpt();

            $output .= '<h4>';

            $output .= '<a href="' . esc_url($link) . '">' . esc_html($title) . '</a></h4>';

            $output .= '<p class="child-excerpt">' . esc_html($excerpt) . '</p>';

        }

        wp_reset_postdata();

    }

    return $output;

}

add_shortcode('wpb_childpages', 'wpb_list_child_pages');