When you import tasks from Microsoft Word, Excel, or Outlook, or an existing tracker, the task hierarchy is maintained.

For more information, refer to Creating a checklist and Copying tasks from existing checklists. 

To realign the order or hierarchy of tasks based on complexity and dependence, use the following options (in the All tasks and Incomplete tasks checklist views):

• Indent and Outdent options: Right-click a task row or select More options  to change the level of a task or subtask. 
  One or both of these options may be unable for some tasks depending on their place in the hierarchy. For example, you can't outdent or indent the first task or outdent a task that's already at the highest level.

• Keyboard shortcuts: With the Tasks field in edit mode, press Tab to indent and Shift+Tab to outdent tasks.

• Dragging: Point to  ​(this icon appears when you hover to the left side of the Tasks field) and drag the task or subtask to the required place.