You can change a task back and forth from manually scheduled to automatically scheduled. However please note the changes that will apply in each case.

Changing auto scheduled task to manually scheduled:
1. Existing Constraint (Type and Date) are removed.
2. Schedule Type will be defaulted to 'Fixed Duration'.
3. Dependencies will remain. They will be 'FYI' only.
4. Fields like Duration, Constraint Type, Constraint Date, and Schedule Type will not be visible from Edit Task Popup. If you add these columns to gantt, they will be non-editable and their values will not impact scheduling.
Changing manually scheduled task to auto scheduled:
1. Task will get rescheduled as per auto logic.
2. Fields like Duration, Constraint Type, Constraint Date, and Schedule Type will be visible from Edit Task Popup.
3. Constraint Type will be 'ASAP'.
4. Schedule Type will be 'Fixed Duration'.

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