Use the Utilities>Transform Vector File tool in the 3D interface. This allows any DXF vector file to have
its Z values permanently exaggerated/rescaled, as well as applying a permanent offset:

1/. Choose the source vector file using the Browse button adjacent to the Input file option in the
Transform Vector File tool .

2/. Enable the Transform coordinates option.

3/. Specify the required Z scale (and/or Z offset). X and Y offsets (and scale and rotation) can also be
specified here, allowing a 3D environment to be populated with DXF objects such as vehicles, ships,
aircraft, etc, to give a sense of scale/proportion. This is particularly useful when creating movies.

4/. Using the Browse button adjacent to the Output file option, specify a new output file name, location
and type. Note that by default this tool automatically creates the output file into the same location as the
input file, with a '_trans' suffix added.

5/. Press the Transform button to run the tool.

6/. Display the new vector file in 3D by dragging and dropping it into the 3D window. Alternatively, add a 
3D Vector branch, and browse for the new file through this.