The Partial Twin Leaf Pier Bottom Connections could be modeled by attaching the Previous full Cross-section to the new Double Leaf CS thru its nodes.
As shown in the picture below, the best practice is to use different node numbers and use rigid links between the nodes.
The Top connections are usually modeled with two individual springs for each Pier Leaf positioned in the respective Right and Left Connection Points, similar to the typical abutments.
Note that for this, the Main Girder has to be subdivided into two additional elements, at the leaf positions.