Hi Dan, as far as I know, the part family creation directory by default is the same as the part file creation (Customer Defaults -> Gatwway -> General -> Directories -> Par file directory). The part family directory in the customer defaults is used to search the part family members the system can't find when NX is in assembly.
From help:
Creating Assembly Part Family Members
When creating or verifying assembly part family members, the system first searches for any parts using the Load Options. If no parts are found, the system searches the Family Save Directory, as specified on the Part Families dialog.
If the Family Save Directory is empty, the system continues to search in the following order:
1.Use the directory specified by the UGII_INITIAL_FAMILY_INSTANCE_DIR environment variable.
2.Use the directory specified for the Part File Directory customer default.
3.Use the default directory.
Regards
Frank.