hi when item fulfillment is shipped, the sales order changes from pending fulfillment to pending billing - it is a built-in functionality of NetSuite. - Can I trigger it by script (not workflow) from a sales order when it is updated?

I haven't thoroughly tested, but from memory it doesn't trigger an SO no matter the

context.UserEventType

https://docs.oracle.com/en/cloud/saas/netsuite/ns-online-help/section_4407992596.html. What I do is have the user event on the item fulfillment and either do the changes from there or task another script to do it in the background.