Answer
Key to parameter fields in ArcPad's Datum Configuration Tool:
Dx Translation along X axis
Dy Translation along Y axis
Dz Translation along Z axis
Rx Rotation around X axis
Ry Rotation around Y axis
Rz Rotation around Z axis
Xcr X Coordinate of Rotation Origin
Ycr Y Coordinate of Rotation Origin
Zcr Z Coordinate of Rotation Origin
The Xcr, Ycr, and Zcr fields are only enabled if the datum transformation method used requires input into these fields.
The dataset parameter is the name of the dataset the user gives the custom transformation. Again, this field parameter is only enabled in the Datum Configuration Tool window for those transformations requiring its use.
The Molodensky_Badekas transformation method is an example of a 10-parameter transformation method.