Just for archival reference I have found what I was looking for. With the 'no-pen' lines selected, (You can create these lines, either with the bÃ©zier tool as Christian suggested or even with the 'box' tool, it does not appear as though the line actually have to come to a full closure either.) you have to go to window, show fill window, click the blue block, "Fill Color", and select the color you want... most likely the white to hid items in layers, and double click it. Voila! Hidden full objects without deleting original data.