It’s important to know that not all sublists in NetSuite are scriptable. Last week in the NetSuite Professionals Slack room, someone was asking how to add to the Contacts sublist on a Vendor record. To answer the question, I went to the Help page titled “Scriptable Sublists” and saw that “Contacts” was not listed there.
“Scriptable Sublists” is a very useful reference page to keep handy. It will help you to identify whether you can script a specific sublist directly or that you’ll need to take a different approach.