It is impossible to move a layer independantly of that layer's mask (the mask
staying stationary). In Photoshop, this can be accomplished by unlinking the
layer from the layer mask, and then moving the layer.

Although you can in effect accomplish the same effect by moving the layer and
mask together, and then moving the mask, it would be much simpler if you could
unlink the layer from its layer mask, like in Photoshop.