Dragging to center collection highlights one item. Release the mouse button to paste over the item.
Dragging to the library or pasteboard collection highlights the entire collection. Release the mouse button to add an item to the collection.
To cut and paste, hold down the Command key while dragging. Release the mouse button to cut the item and paste it over (or into) the highlighted item or collection.
To highlight a single destination item in any collection, hold down the Option key while dragging. Release the mouse button to paste over (or into) the highlighted item.
To copy all the items in a collection, drag a panel (below a collection). To copy into another collection, release the mouse button over another panel. To remove all the items from a collection, release the mouse button on the trash.
