The Product Configurator application currently (tc11.4 or lower) has not the functionality similar to the "Modular Variants" or the "Variant Item".
It's on the roadmap to built this and if you want details, you need to contact the Product Manager.
One workaround would be to create manually a CC (Collaboration Context) object with the BVR of the (top) Assembly and an SVR to configure the product to a 100% configuration. The CC object can be created in MPP (Manufacturing Process Planner) and if you untoggle the "Show unconfigured Variants" icon and then save this CC, it will be included in the CC object, so next time you don't have to worry about this toggle.
Other workaround would be to use an "order" item (maybe set this up and tweak it in BMIDE and deploy it).
And after you have configured the assembly, copy all BOM lines to this order item. (this method only works if you have just variability on the 1st level of the original assembly)