From GTAC
The Local Scale, Simplify Body and Edit Face commands are hidden in NX5.0.2 and
higher. You can add them back to the user interface with the following:
Local Scale: set the variable UGII_DMX_NX502 = 1 in NX502. In NX503 and
higher, use Tools -> Customize --> Commands tab --> Insert...
I had the same question and was really dissappointed that such a powerful tool as "simplify body" was removed. The "delete face" command is more constraining. I contacted GTAC and they helped me re-enable the "simplify body" command in our NX 5 environment. "Delete Face" is far more tedious...