That is the [List Item] component. In the latest GH versions you can zoom in on the component and add additional outputs for +1, +2, +3 etc. and -1, -2, -3 etc.
Thanks Clemens,
So the overlapping part of each thickness h has the bending stiffness proportional to 2*h^3=(1.26*h)^3, not (2*h)^3, I understood.
Best regards,
Jaeman