Hello and sorry for the late reply.
Just to clarify, are you refering to the possibility to declare BBParameters within a custom class, or the possibility to create a Blackboard scriptable object asset?
If the later, I have attached for you here a unitypackage, which will allow you to create a Blackboard scriptable asset (right click in the project assets Unity window). Please use only for testing purposes at the moment).
Please let me know if that is indeed what you were after.