Coordinates can be displayed in an alternate coordinate system by selecting Tools > Geospatial > Select Alternate Coordinate System. A dialog similar to the geographic coordinate system selection dialog is displayed.

Select the appropriate alternate coordinate system.

Make that coordinate system active in the Auxiliary Coordinates dialog as above. If the ACS position option is enabled then the new readout will be in Auxiliary Coordinate system units.

Key-in: MapCSUtilities SelectAltCoordSys