Scenario: On the Process canvas, start creating a new task and remove any solvers on the task (to set it as a milestone). At this point the logical thing would be to assign a deadline date/time.
However, there is no ability to assign a deadline that I can find (the field doesn't exist in the task creation dialog.
If I save the Process canvas (which reverts the Process view and then I have to go looking for the task again), then edit the task, the deadline field is there. It's just not there during the task creation.