Yes, I second this! We have a lot of calls from customers who are concerned they didn't receive discount because automatic discounts don't come through on packing slips like coupon codes do. I confirmed with support that this feature is not currently available and it was suggested that I post here.
I also would love this feature to happen. I talked to support forever who kept saying I can custom code it in but I do not see how that is possible at all. I tried the [Adjustment] call tag and it didn't work but they kept saying there was a way but couldn't tell me what it was...
We also have this issue. We have a free shipping over $ amount and on the shipstation packing slips the shipping automatically populates and people are confused.