Details
How to Set a Custom Default Assembly Load Options File in NX.
Solution
Locate the NX install folder and the sub-folder called UGII.
Open the file ugii_env_ug.dat with Notepad or equivalent and do not use Microsoft Word as it adds hidden control characters which will cause problems with the file.
NOTE: NX may not start if this file is not in its original ASCII text format.
In the ugii_env_ug.dat file is the environment variable "UGII_LOAD_OPTIONS=", which needs to have the complete path and the file's name. This would include the drive letter, colon, folder path with slashes and the custom saved assembly load option file name with the extension (.def).
Please note that the Assembly Load Options dialog uses Dialog Memory (recognized by the Reset button or semi circle in the top right corner). If you use the dialog to specify a different file, then dialog memory will remember that, and that file will be used to supersede the default Load Options setting. The "Reset" button can be used to specify the default value again (top right corner of the dialog).
Notes and References
Hardware/Software Configuration
Platform: INTL64
OS: window
OS Version: 764SP1
Product: NX
Application: ASSEMBLIES
Version: V8.5
Function: ASSEMBLY_MODEL
Ref: 001-9064382