How to setup Priority for Alternate item-structure selection in Constraint supply plan

Summary:

I understand that production priority can be setup at work definition level and it can be used to pick an alternate work definition, BUT is there a way to do the same at the item structure level. I do not see this attribute neither in the manufacturing setups nor in FBDI and nor in simulation set either. In other words are we saying that in order for the system to recommend alternate BOMs we MUST UPLOAD alternate work definitions too.

We are getting the ERP data from EBS and Somehow we have managed to work our UNCONSTRAINT plans without the work definitions (only BOMs)