So this question probes "several layers deep" on a Project and Item record.

THE CONTEXT:

I have a Service Item for Sale with an active Item Option. When generating a stand-alone Invoice I can define that Option on the Item rows of the Invoice.

However, I primarily use this Item as the Service Item when assigning resources for various Project Tasks. (Service Items on Project Task assignments are a seamless way to rollup all Project Resources' billable time entries against Project Tasks on a monthly Invoice - I love this functionality!)

THE PROBLEM:

I cannot seem to define the Item Option while applying the Service Item to the Project Task Assignment. This means this field is not set when the Billable Time Entries I apply to a new Invoice get rolled up into the Service Items. When I try to Edit an Invoice to set the Item Option after-the-fact, the Billable Time Entries are shown and the Item Rows are empty (as would be expected).