I'm using .23 preview ... I did some more testing and stairs work as long as you don't use the ! to try to add a single stair. It seems the ! that are broken on the stair material box not the entire thing as I had thought before :p
Never Underestimate the Power of Stupid People in Large Groups
Gotcha. If you need building blocks, create a row of dummy stairs with the coordinate commands. Then use the 'dupe command to copy the blocks into your back.
Wipe the dummy stair.
Now you have stair building blocks you can place by hand.
I used this trick, mixed with the auto-stair command to create curved staircases. You basically create the stairs and cross them using the World Builder. Then where it intersects, you add and remove blocks until you get a nice curved staircase.