Are you asking about Designer or with dyanmic vdbs? The approach would be similar for each.
In the dynamic case you would need to add 1 model for each schema and then in the import properties limit the import to only those objects matching your desired schema (schemaPattern=schema_x). You would also tell the import to not use fully qualified names (useFullSchemaName=false). Just be sure to use the same translator/connection for each of the models coming from the same database, so that the engine will know that they can be treated as a single source.
Thank you so much! Your solution works great! =)