Laura,
I think this may be a case for which no option is offered by the Stair Landing component. You can have monolith Landings, but you cannot have Monolith Landings the bottom of which is a Steel profile.
If I had to do this I would probably model it using a Monolith Landing, then Model that Steel Profile beneath it and then use the "Subtract with Downward Extrusion" SEO with the Steel Profile s Operator and the Monolith Landing as Target.
Since the depth of the Landing is not constant, maybe you would need two Profiles for the different depth Landing portions. Or you would have to model it using the Morph Tool.
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