I'm looking to create a custom record to "hold" information from a Sales Order to later process into an item fulfillment. I'm familiar with transform via SuiteScript, but not sure on the Custom Record sublist. Is this just building a new list out of the Sales Order line items (exclude main line for instance)? Or do I need to perform my own mapping to the custom record, given the custom record is not a Transaction type?

How much information are you wanting to "hold" from the SO record? Can you go with custom fields on the sales order vs having to use a custom record? For the custom record you have complete control over the fields you wan, you just need to make sure to have one custom field on the custom record as a list/record type referencing the transactions list.

OK this makes sense. I'll see if I can go the transaction list reference route, otherwise, I'll just pull the fields I need from the SO. Effectively, the process here is to collect information from the currentRecord of an Item Fulfillment that will then get processed by an external system. From there, that system updates the custom record and finally SuiteScript to Transform the SO to an IF with the processed information. In that sense, it really doesn't need to be anything from the SO other than thinking it would make my life easier