Hello,
and thank you for reaching out to us with your inquiry.

I tried many different action combinations in the Access Rights setting and I haven't been able to unlock the discount per row.
Considering you would have a discount field affecting the Subtotal only, HAL is the only way to get this.
However, I see the value of your customer's request and I strongly suggest to make a wish about it.

Best Regards
Giuseppe
HansaWorld Italy