Structures have a primary element listing based on the structure type defined for the record. Bridges have a list of bridge elements available to be added to the element hierarchy, for example.
You can also use the Elements Settings tab to add secondary element listings to a structure's element hierarchy. This enables you to build a hierarchy made up of multiple structure types.
Open the Structure, then in the Structure menu, click Elements. Click on the Edit Elements link, then on the Settings tab.
The Primary Element Listing Type will show at the top of the list. This cannot be edited or deleted. Click the Add Secondary Element Listing button to to include construction and elements from other structure types.
Choose a secondary element listing from the Element Listing drop-down. The same element listing cannot be added more than once. Complete the optional Notes field and click Update. In this example a Retaining Wall listing is added to a Bridge Type structure.
Returning to the Edit Elements page, you will now be able to add in Retaining Wall construction and then elements to the hierarchy. First click on the Construction/Elements folder, then add in the construction (in this case a Retaining Wall Panel).
From here you'll be able to add in the elements from the secondary element list.