In order to add a recipient to a specific email type, use below filter by adding it to your themes functions.php file. Make sure to change the YOUR_EMAIL_ADDRESS to the desired email address.

/**
 * Add recipient to Customer Credit Note email.
 *
 * @param string $headers WooCommerce email headers.
 * @param string $status  WooCommerce email type.
 *
 * @return string
 */
function add_recipients_to_customer_credit_note_email( $headers, $status ) {
	if ( 'bewpi_customer_credit_note' !== $status ) {
		return $headers;
	}

	$recipient = 'YOUR_EMAIL_ADDRESS';
	$headers .= 'BCC: <' . $recipient . '>' . "\r\n";

	return $headers;
}
add_filter( 'woocommerce_email_headers', 'add_recipients_to_customer_credit_note_email', 10, 2 );