Is there a way to load values for a specific segment outside of the form?
Yes. There is an workaround to load code combinations. Outside of manually creating the code combinations, ADI may be used to load zero dollar journals to create new code combinations. Please be aware that Dynamic Insertion should be enabled and all account segment values need to exist before the new account code combinations will be dynamically created. Enhancement Request Bug 2974057 has been logged to provide an API to load account code combinations.