Changing the Center of Rotation
A selected shape will show a gray semi-transparent circle connected to the rotation handle. This gray circle indicates a selected shape's Center of Rotation and can be changed to any desired point within the shape's bounds. By default, the option to change a shape's Center of Rotation is not enabled.
Use the Handles Settings popup menu to to enable the "Center of Rotation" handle.
A new handle will replace the original semi-transparent circle once this option has been enabled.
To alter the Center of Rotation, drag the newly visible handle to a desired location.
The shape will rotate around the new point rather than its natural center once it has been set.