There’s currently a way to lock a box to the background. But no way to do similar for cards, such as to put them all the way in the background or the foreground, or keep them at the same Z axis, or send them backward a layer, etc.. The only way to manipulate card Z axis currently is to drag them, which brings them to the foreground. So if you have cards layered in a specific way, then want to move one of them, it might mess up the ordering.