As this is not something you can do in iModel, there is a trick to get this added to your layout.
1. First go ahead and piggyback your trusses as you normally would.
2. Then bring in the piggyback you just created into iDesign and piggyback it again to the desired upper piggyback height.
3. Once you design this save as a new truss.
4. design the rest of the trusses as you normally would.
5. Get the height needed by doing a bearing info on your upper piggyback truss and enter a Flat plane at that height in iModel.
6. Once you get the flat plane solved you can add trusses by picking the regular add trusses and make the family type valley.
7. Go into iDesign and grab the upper piggyback truss that you saved and run it and save it to layout over the trusses you just put in.
8. Now you will have the base, regular piggyback and the upper piggyback truss all on the layout to label for your customer.
Please reach out if any further assistance is required.
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