Use the Multistory: Select Levels tool during stair creation to create a multistory stair on selected levels.
 Circulation panel
Circulation panel
 (Stair), and create the desired stair component.
 (Stair), and create the desired stair component. 
   Edit panel
Edit panel
 (Multistory: Select Levels).
 (Multistory: Select Levels). 
  For example, use a selection box or press and hold Ctrl while clicking the levels. Press Shift and click a level to deselect it.
The selected levels highlight, but you will not see the stair extended until you click Finish.
 (Edit Stairs) to return to creating the component-based stair.
 (Edit Stairs) to return to creating the component-based stair. 
   (Finish).
 (Finish). 
	 The component-based stair is created and the multistory stair is generated on the selected levels.