You can drag and drop almost any kind of object in Opacity. This includes frames, layer, variables, transforms, factories, images (from the Quick Info panel), vectors and pixels (when they are selected). You can also drag in images from other applications, including the Finder. You can copy and paste most of these objects to accomplish the save effect.
When you drag images, vectors, and pixels to the canvas, they are inserted into the current layer of the current frame. They are centered at the position where you drop them.
When you hold the Option key while drag-and-dropping objects, the objects are copied (instead of moved) to the destination.