DSS does not have an equivalent Scala API, which indeed is why you were having trouble figuring out how to do this. Since we have a fully supported Python API, I would suggest sticking with Python/PySpark for any actions that use the DSS API. For other types of transformations (i.e. if you are transforming columns in your dataset, filtering your dataset, adding columns etc.) these types of operations don't use the DSS API, so you could do dataset transformations either in a PySpark recipe or a Scala recipe, whatever option is easiest for you.
I hope that information makes sense. Please let us know if you have any questions about this.