Looking at this again, the risers of your oval stair all emanate from one central point.
So create a large circular stair and then adjust the stair boundaries (not the baseline - leave that circular) and you may be able to get what you want.
Add nodes to the arc and adjust the edges to match the curve of your oval.
I just had a go tracing over your image but I can't get the top point of the stair to pull down enough to match your oval.
Close but not quite.
It seems there is a limit to how yo can adjust the boundary - which I am a little surprised at.
Yours may work as you have a more accurate drawing rather than an image I copies from the forum.
An alternative would be to create a slab with an oval shaped hole and the Solid Element Operate this with the stair to cut the shape away.
Barry.
One of the forum moderators.
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