You could change the outline structure by using indent/outdenting buttons on the toolstrip. If the indented/outdented task is a summary task, all its children will be done, too. Things are simpler if the selected task is a regular task.

Indent Task

While the previous task has outline level greater than or equal to the selected task, the selected task are still able to indent. The indented task will be adopted by the upper nearest task that has the same outline level with it. If supposed parent is regular task, after indent the selected task, that parent will become a summary task

Outdent Task

While the previous task has outline level less than or equal to the selected task, the selected task are still able to outdent. The outdented task will be adopt as a new child of its grandparent. If it is the last child of its parent before outdent, after that, the old parent will become a regular task.