I would like to have a numbering (sequence) for credit notes (refunds) that is separate from the sequence for invoices. In odoo Online, v10.

Googling, I realised this is a new feature in v10. There is supposed to be a "Dedicated Refund Sequence" checkbox available on Journal templates, but I don't see any such thing. I am looking at Configuration - Journals within the Accounts module. Should I be looking somewhere else to see this option? I hope that such a simple setting doesn't require any coding.