This is a Request to make placing stacks, and moving the same items into stacks easier. By double-clicking on the selected item which you want to group.
Example: You have 4 half stacks of wood, and you want to make them into 2 stacks-ish. You just double click on that item, and all of them come together into the item which you double clicked on.
The advantage of this would be that you wouldn't have to keep dragging and dropping items together, both a long and boring task.
Thanks.