The desired new z-coordinate may be entered in the setup panel of the 2D-display, or in the z-value panel of the 3D-control panel. The latter is more convenient, since this panel is always visible. Values between -32768 and +32767 are legal.
With the mouse all units are selected which are to receive the new z-coordinate.
With the key sequence U 3 Z (for Units 3d Z) the units are assigned the new value.
Afterwards all units are deselected.