send a copy of "vendor notify shipped" email to the admin

functions.php

add_filter( 'woocommerce_email_headers', 'custom_vendor_notify_shipped', 10, 2);
 
function custom_vendor_notify_shipped( $headers, $email ) {
    if ($email == 'vendor_notify_shipped') {
        $headers .= 'BCC: Your name <your@email.com>' . "\r\n";
    }
 
    return $headers;
}