Lets you enable rotation or scaling of an object or objects around the center of the current coordinate system.
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Main toolbar > (Use Transform Coordinate Center), on Use Center flyout
The Use Transform Coordinate Center button is available from the Use Center flyout.
When you designate another object as the coordinate system with the Pick function (see Specifying a Reference Coordinate System), the coordinate center is the location of that object's pivot.
The axis tripod shows the center that is currently being used.
Note: The transformation center mode is set on a transform-by-transform basis, so select the transform before you select the center mode. If you do not want the center setting to change, turn on Customize menu 
Preferences General tab Reference Coordinate System group Constant.
Preferences General tab Reference Coordinate System group Constant. 
An example of the World coordinate center