Añadir un tab adicional a un producto de WooCommerce

Este código es de Adding Custom Text Area to WooCommerce Product – WordPress Development Stack Exchange

Funciona hoy. No sé mañana.

Lo de siempre. Puede añadirse a un plugin, theme o… como snippet usando un plugin de snippets.

// Add custom Meta box to admin products pages
add_action( 'add_meta_boxes', 'create_product_technical_specs_meta_box' );
function create_product_technical_specs_meta_box() {
    add_meta_box(
        'custom_product_meta_box',
        __( 'Technical specs', 'cmb' ),
        'add_custom_content_meta_box',
        'product',
        'normal',
        'default'
    );
}

// Custom metabox content in admin product pages
function add_custom_content_meta_box( $post ){
    $product = wc_get_product($post->ID);
    $content = $product->get_meta( '_technical_specs' );

    echo '<div class="product_technical_specs">';

    wp_editor( $content, '_technical_specs', ['textarea_rows' => 10]);

    echo '</div>';
}

// Save WYSIWYG field value from product admin pages
add_action( 'woocommerce_admin_process_product_object', 'save_product_custom_wysiwyg_field', 10, 1 );
function save_product_custom_wysiwyg_field( $product ) {
    if (  isset( $_POST['_technical_specs'] ) )
         $product->update_meta_data( '_technical_specs', wp_kses_post( $_POST['_technical_specs'] ) );
}

// Add "technical specs" product tab
add_filter( 'woocommerce_product_tabs', 'add_technical_specs_product_tab', 10, 1 );
function add_technical_specs_product_tab( $tabs ) {
    $tabs['test_tab'] = array(
        'title'         => __( 'Mer information', 'woocommerce' ),
        'priority'      => 50,
        'callback'      => 'display_technical_specs_product_tab_content'

    );

    return $tabs;
}

// Display "technical specs" content tab
function display_technical_specs_product_tab_content() {
    global $product;
    echo '<div class="wrapper-technical_specs">' . $product->get_meta( '_technical_specs' ) . '</div>';
}