We use lists to track summer maintenance periods, certain tasks may have been planned for that maintenance period but then get deferred to a later maintenance period and added to a new list. We don't want to transfer the tasks to the new list, just add them, but we don't want task updates on the new list to change the old list. Is there a way to lock/freeze an older list that shares tasks? Or even better, a way to view a list as it was on a past date using the extensive task history? If this is not planned, can we at least get the task history from the API so we can do this ourselves?