When creating a process definition in the Process Definition window, you can drag and drop activities and steps using the Reorder 
button. This feature is particularly useful for complex processes that change often and/or contain many steps and activities.
When you select a step or activity in a process definition and then select the Reorder button (see the following illustration), the Step & Activity Drag Drop dialog displays. The dialog shows steps and activities in a tree view (hierarchy); steps are listed on the left and the activities for each step are nested underneath.
Drag the step or activity to a new location. The dialog indicates the item you are dragging and the target location.
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If you try to drag and drop a step or activity in a location where it can's be reordered in the hierarchy, you'll see the message Cannot drop here, as shown in the following illustration.
