Has anyone created a script to automatically copy the bin from a CUSTOM field from the sales order and work order TO the item fulfillment and assembly build/work order issue at the time of creation of the latter? Is it doable? How complex it is?

You cannot assign the inventory details at the time of the creation because the record won't save. Inventory details are required from item fulfillment.

Yes, that's why we plan to use custom fields on the SO and WO to store the bin. Then, supposedly, the script will pick up the value from the custom field to the actual inventory detail at the time of creation of the Item Fulfillment and Assembly Build/Work Order Issue.

That's what I am saying. You cannot do it on the item fulfillment because it is required before saving the item fulfillment. And client script doesn't have access to inventory detail.

Thank you so much!