Currently, Biome API is not reliable for adding to dimensions. BiomeSelectors#foundInOverworld, for example, would probably break in modded world types. The best solution to this is to allow Structures to have a specialized setting in Structure API to do this check. In FabricStructureImpl, it gives us access to not adding StructureConfigs by checking the world's RegistryKey.
In FabricStructureBuilder, we would add a dimension method that allows modders to specify what dimensions to add, but I'm unsure of how to go about this. We could let them add a collection of Identifiers, or modders could give a Predicate<RegistryKey>, or something, just unsure of how to go about that.

ima do a Predicate