This article is done with the Software version EinScan HX126.96.36.199
The created projects have automatically a rotation centre. When you click and hold the left mouse button the object will rotate like the mouse is moved. When the left mouse button is released, the object also stops rotating. You can see the workflow bellow.
The rotation centre can be changed by right-clicking in the window. A new window pops up. The second last point is called "Set Rotate Centre", when you click on it the function is started. Now click on the are on the object where you want to set the new rotation point. After you click on the area the new rotation centre is set. You can see the workflow bellow.