As stated in the above referenced link, just use the...
Analysis -> Measure Bodies...
...function and if you toggle ON the 'Associative' option, there will be a point created at the centroid (Mass Center) of the selected solid body. Optionally you can also have the system create a Coordinate System representing the major X,Y,Z principle axis.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA Siemens PLM: UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.