The refound options are not enough.
1. I suggest that it will be possible to create a refound note without necessarily going through an invoice.
2. actualy, when you create a refound, you must pay the amount of the bill, but sometimes I do not refund the bill in totality.
3. Today, the payment of a credit note can not be done in two different kind of payment. It would be necessary to be able to split the payment.