When doLimitedCrafting is set to true it is possible to duplicate items in both the personal crafting and crafting table boxes.

This works with both stackable and non-stackable items.

To reproduce. set doLimitedCrafting to True. For non stackable items, 2 will work. For stackable items, fill all slots with the item.

Click and drag like you would be splitting a stack. upon dropping the item in its original slot. double click. That item is now duplicated.

Video Demonstration https://www.youtube.com/watch?v=8dAQJp--k6w