In MS Project or Primavera, the parent task depends on the duration of all the sub tasks. This is basic need for a Project Manager. We often create a parent task and add several subtasks with known start and end date. For example,

Creating A certain Document - > Parent Task

Prepare a draft - Subtask 1

Review the draft - Subtask 2

Update the draft - Subtask 3

Review and release - Subtask 4

Now, it's easier to put start and end date for all the subtasks, and the parent task start and end date will depend on the subtasks.

In case one gets delayed or finishes early, we can adjust the subtasks and this should also update the dates for parent task.

Please include this for the tasks management.