This is a very secure function and only very few users will have access to this screen.
Go to Job -> Management -> SuperUser edit task details -> Choose a task
in the following screen you will be able to edit every aspect of a task within ClickHome.
Resetting the Tasks from completed or planned state to unplanned: (Remove from the My tasks).
P.S: You are better of making sure that the Task that is being reset will be revisited in the workflow (else it may always remain unplanned)
To be able to access Super User Edit, the user will need to have certain security permissions for the relation that they need to make changes on.
Also the user may need to have operation code 7305 to accept future task.