I was able to place an empty rain coat in my inventory. Then drag and drop items into that rain coat (coat takes 2 slots in my inventory/holds 4 slots)

I was not able to fill the rain coat and place it in my inventory.

The rain coat must be in the same container as the item 'dragged and dropped' from. I tried to drag an item from my pants to the raincoat stored in my backpack and I could not move the item, (but if the item is in the backpack it would drop in)

Also if I opened food in my inventory (not my hands) it would move into the slots of any empty 'stored' container IE opened peaches in my back pack.... I thought they disappeared but they moved into my empty raincoat in my backpack.