Currently, if no IDT fields are set on any strand, then write_idt_plate_excel_file will not export any of them. The way to give them a default IDT field for export is to set their IDT fields, either directly or by calling Strand.set_default_idt.

It would be convenient to have write_idt_plate_excel_file have an option to temporarily set these for all staples (not scaffold), i.e., just use a default value for idt without setting it, so that write_idt_plate_excel_file can simply be called without having to first modify the Strands.