Add the variable "TTN return delivery"

Good afternoon.
This field is not directly related to the process, unlike the "Delivery Note" field (order.deliverynote).
For correct implementation, it is necessary to check the presence of a variable in the template, as well as the delivery method and the presence of the return delivery TTN in it (where the number may be present in several integrations with delivery services).
Implementing such a variable, taking into account the above checks, will take about 3 hours both for document templates and for processes and letters.