Our add-ons go as far as properly registering the transaction ID in Gravity Forms, apparently Gravity Forms does not allow a shortcode (merge tag) for transaction ID (or payment status/date) in notifications, We have not seen the official PayPal, Stripe or Authorize.net plugins have it either. You can perhaps try to manually fetch them from your entries using the code in the link below:
https://stackoverflow.com/questions/14558054/transaction-id-in-email-notification-gravity-form