If you want to move documents from one collection to another, proceed as follows: Press the “ALT” key (“option” for Apple Mac) and keep it pressed until the last step. Begin the drag&drop process. Right-click a document in a collection and drag it over to the target collection. The target collection turns orange. Release the mouse button. The document is now moved to the target collection and removed from the source collection. Now you can release the “ALT” key.