How to add a phantom item to a alternate structure

Summary: How to add a phantom item to a alternate structure

Content (please ensure you mask any confidential information):

Hello,

I have a finish good and this finish good has a primary structure, and within this primary structure, we have a phantom item, which also has a primary structure.

We want to create an alternative structure for the finish good and set an alternative structure for the phantom item.

But the system automatically sets the phantom item’s structure as primary.

I would like to know how can I choose which structure to use.

Version (include the version you are using, if applicable):