要回答您的第一个问题,以post meta这种方式让您的»bookauthor«可以回显/显示出来。如果您$id在代码中正确定义了变量-或可以如下所示进行操作。
该代码应回答您的第二个问题,即如何通过钩子将第二个标题行插入产品页面woocommerce_single_product_summary。只需添加您的额外信息,如下所示:
    function wpse116660_wc_add_2nd_title() {
        ?>
        <div class="2nd-tile">
            <?php echo get_post_meta(get_the_ID(), "bookauthor", true); ?>
        </div>
        <?php
    }
    add_action( 'woocommerce_single_product_summary', 'wpse116660_wc_add_2nd_title', 6 );
为了让您的自定义帖子元更加舒适,您可以执行@ pl4g4和@brasofilo建议的操作,并将metabox添加到产品编辑屏幕中,但是当然没有必要,您似乎知道如何使用标准的wordpress 自定义字段metabox。
您可以像这样添加元框,该代码基于add_meta_box wordpress Codex页面上的第一个示例。
/**
 * Adds a box to the main column on the Post and Page edit screens.
 */
function wpse116660_wc_2nd_title_mb() {
    $screen = array( 'product' );
        add_meta_box(
            'wc_2nd_title_mb',
            __( '2nd title', 'your_textdomain' ),
            'wc_2nd_title_inner_mb',
            $screen,
            'advanced',
            'high'
        );
}
add_action( 'add_meta_boxes', 'wpse116660_wc_2nd_title_mb', 0 );
/**
 * Prints the box content.
 * 
 * @param WP_Post $post The object for the current post/page.
 */
function wpse116660_wc_2nd_title_inner_mb( $post ) {
  // Add an nonce field so we can check for it later.
  wp_nonce_field( 'wc_2nd_title_inner_mb', 'wc_2nd_title_inner_mb_nonce' );
  /*
   * Use get_post_meta() to retrieve an existing value
   * from the database and use the value for the form.
   */
  $value = get_post_meta( $post->ID, 'bookauthor', true );
  echo '<label for="bookauthor_field">';
       _e( "Bookauthor", 'your_textdomain' );
  echo '</label> ';
  echo '<input type="text" id="bookauthor_field" name="bookauthor_field" value="' . esc_attr( $value ) . '" size="50" />';
}
/**
 * When the post is saved, saves our custom data.
 *
 * @param int $post_id The ID of the post being saved.
 */
function wpse116660_wc_2nd_title_save_postdata( $post_id ) {
  /*
   * We need to verify this came from the our screen and with proper authorization,
   * because save_post can be triggered at other times.
   */
  // Check if our nonce is set.
  if ( ! isset( $_POST['wc_2nd_title_inner_mb_nonce'] ) )
    return $post_id;
  $nonce = $_POST['wc_2nd_title_inner_mb_nonce'];
  // Verify that the nonce is valid.
  if ( ! wp_verify_nonce( $nonce, 'wc_2nd_title_inner_mb' ) )
      return $post_id;
  // If this is an autosave, our form has not been submitted, so we don't want to do anything.
  if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) 
      return $post_id;
  // Check the user's permissions.
  if ( 'page' == $_POST['post_type'] ) {
    if ( ! current_user_can( 'edit_page', $post_id ) )
        return $post_id;
  } else {
    if ( ! current_user_can( 'edit_post', $post_id ) )
        return $post_id;
  }
  /* OK, its safe for us to save the data now. */
  // Sanitize user input.
  $mydata = sanitize_text_field( $_POST['bookauthor_field'] );
  // Update the meta field in the database.
  update_post_meta( $post_id, 'bookauthor', $mydata );
}
add_action( 'save_post', 'wpse116660_wc_2nd_title_save_postdata' );
               
              
add_action与6作为优先事项是什么会把字幕权的正规标题后(其中有5个优先级)。万一OP不想添加自己的metabox,我已经写了一个字幕插件来保存数据。