We use Planner Tasks at very high level, for example to track a Change, Initiative or Problem. We then have the Planner Board as a high level view of these within various buckets indicating stages and labels indicating type. But within each of these Tasks there may be sub-tasks we want to track - like milestones. It would be good if this was possible, and then with those tasks integrated with Outlook Tasks and To Do we can get different ways to view work load and manage work. Of course, if a Gantt chart is ever integrated these sub-tasks could be optionally included within the task timeline. I know we are getting into MS Project area...but Planner offers a lot in terms of an easy to use visual Team resource management across a number different types of activities which Project does not.