The draggable axis spans is a very useful function for me so that I can apply some mathematical calculations with only the data that is inside the marked region.

One further feature would be very helpful for me:
Click in the PlotHSpan (or PlotVSpan) region (maybe with a mouse modifier key and the right mouse button since all of the left mouse buttons are already used with modifier keys) and drag the complete region to the left or right (PlotHSpan) or up or down (PlotVSpan).
The big advantage in contrast to drag the axis separately is that the width of the region will be maintained.