I am assuming this is AC21 or 22.
ARCHICAD has element types, such as Wall, Column, Door, Window, Stair, Railing, Object, etc.
So an Object is an element type that is created with the Object Tool.
A Stair is an element type that is created with the Stair Tool.
When Grasshopper wants you to set an Object, it wants you to set an element created with the Object tool.
Maybe the confusion comes from the fact that in some other applications everything you create is called an "Object", while in ARCHICAD everything you create is called an "element".
So in ARCHICAD, an Object is a specific type of element.
In ARCHICAD you do not have a "Stair" object. You have "Stair" elements and "Object" elements. It is a different nomenclature.
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