Add this code to your child theme’s functions.php file or via a plugin that allows custom functions to be added, such as the Dessky Snippets plugin. Please don’t add custom code directly to your parent theme’s functions.php file as this will be overwritten completely when you update the theme.

Use the following snippet to add a custom global product tab.

/**
 * Add a custom product data tab
 */
add_filter( 'woocommerce_product_tabs', 'woo_new_product_tab' );
function woo_new_product_tab( $tabs ) {
	
	// Adds the new tab
	
	$tabs['test_tab'] = array(
		'title' 	=> __( 'New Product Tab', 'woocommerce' ),
		'priority' 	=> 50,
		'callback' 	=> 'woo_new_product_tab_content'
	);

	return $tabs;

}
function woo_new_product_tab_content() {

	// The new tab content

	echo '<h2>New Product Tab</h2>';
	echo '<p>Here\'s your new product tab.</p>';
	
}