Step 1: Have enough stacks in your inventory to be able to scroll

Step 2: scroll down any amount

Step 3: while scrolled down, drop a stack from the top visible row of your inventory

Result: It will drop that stack, as well as all the stacks above it in the same column.

Bonus edgecase testing: I tried it in the column that holds my burrow certificate, and got the "You only get one of those!" etc message, and it did not drop, but remained in my inventory as normal.

Addendum: When you drag to the ground to drop, it drops the stack selected as well as those above. However, if you right click and select "drop," it *only* drops the stacks above, not the selected item.