Hello and Welcome to Budget 101, MissDaisyMae! Good to have you here. Enjoy!
Yes, I believe you can add scented oils to the laundry sauce. I have read no reviews of doing so for this recipe, however I have seen other homemade laundry detergents with scented oils added. I see no reason that this would be any different.
Hope this helps. Any other questions, just ask. Thanks; Virginia