I’ve inserted a Polygon Object in my non-sequential system to use it as a rotating polygon mirror. I would like to rotate this object about its center axis (which currently points along the Y direction) .  Changing its Tilt About Y parameter rotates the polygon about its first face changing the X-Y position of the polygon too .  Is there a way to rotate instead about the center of the polygon so that it spins on its axis  ?

[Mod note: moved to more appropriate forum for OS-related discussions.]