// Unset the default, so that it no longer applies
unset($GLOBALS['TYPO3_CONF_VARS']['SYS']['messenger']['routing']['*']);
// Set Webhook-Messages and DynamicsMessage to asynchronous transport via RabbitMQ
foreach ([WebhookMessageInterface::class, MyCustomMessage::class] as $className) {
    $GLOBALS['TYPO3_CONF_VARS']['SYS']['messenger']['routing'][$className] = 'amqp'; // The tags identifier defines in Configuration/Services.yaml
}