Supply stockpile option “Copy from slot” seems not to work properly.
Not sure about all the slots, but it seems that problem is reproducible for “not top level” slot.
I mean that I use option “copy from slot” option on a stock pile, and it works well on top level slot - e.g. Fit Body. But it does not on lower level slots.
My example is “Fit Door panels” and I click “copy from slot” in a stock pile menu, and result is “door panels”, but not resources used by “fit door panels” slot.