I would like to be able to put furniture in the attic without having to go to an empty house, place down the furniture, and pick it all up. It can be quite a hassle, especially for one piece of furniture.
You don't have to do move all. If you just want to move something to your attic from either your backpack or from your house, open the attic tab by hitting on it when your item selection is open and then you should have three tabs: attic, house and backpack. You can move items between all three by selecting it in the appropriate window.
What's stopping you? You can place any housing items, pets or seeds that are in your backpack in the attic. Not sure why you think you need to place items and pick all up. Open the Place Objects window in your house. Click Open Attic. Click the Backpack tab. Select an item and click Move to Attic.