Hello Ebech,
Presently, you can set Due Date to the same day the task is scheduled, by setting the “Due Date” checkbox.
It’s not possible to set the date in the future relative to the scheduled date.
A workaround might be to set the “Due Date” checkbox, and then, as the action becomes active and due, change the due date to +14 days manually. This can be done very quickly via a command :d 14. Here’s more commands if your are interested.
That said, this is a valid use case that is not supported. I will check if it’s already in the backlog, and add it if it isn’t.