How to Use Default Arguments in a Type Class

There's a difference between do I want this parameter to be filled in by the scope, or do I want the function to provide me with a default. The common use case that I see for type classes is around generic transformers. You'd have to maybe make it a type alias to something. So I think that type aliases are just just an alias. But I think maybe opaque aliases and Scala three may work for this, but be I.