In Didger, the Z-level is set to the Primary ID by default. If you have your Z values in the Primary ID field, then Didger 4 will automatically export these to the Z level field in the DBF file. If you entered your Z values in another ID field, go to File | Data Attributes and make sure the Z-level is set to that ID field. Click OK and export the SHP. The Z values from whatever ID field you specified will be exported as the Z level in the DBF file.
Updated September 5, 2018