Just came across a very simple work-around on this... Not sure if this completely works for you, dpaul, but for those of you wanting to have some way to track an RMA like you can track a sales order:  Just create your credit memo, but before you save it, click the "Mark as Pending" button near the print button.  This makes the credit memo non-posting and this even prints out on your template like a watermark that it is pending.  You may want to create a new template to use just for this, but after the material is received back to you, just click that button again ("Mark as Final") and it becomes a posting credit memo again.