Hi Piotr,

Yes, this is possible but you have to remove the risers first otherwise the editing will not be done as it cannot overpass the risers.

just select the nose of any step and right-click. This opens a menu and you select step shaping. There you should have your drawing of the steps. 

Select one drawing. Select the apply button and use apply to all odd steps and for the next all even steps.

regards

Michel