Your sentence was not added because the following already exists.
Erläuterung für Nichtmuttersprachler: „Schönes“ wird angefügt, um die Frage „Was machst du da?“ freundlicher und nicht so inquisitorisch erscheinen zu lassen.
I read your comment.
What would "Schönes" be parallel to, if you substitute it with a word in English or in any other foreign language of yours?
Should there be a comma between "da" and "Schönes"?
This is something rather idiomatic, I would think, and cannot easily be copied.
If you change things round a bit, the sentence would maybe read like this: Was für eine schöne Sache machst du da?
You would only have a comma before Schönes if it stood for a person you were addressing, like an equivalent to "darling" for instance, but then the sense would be different: What are you doing there, darling? But this is not what the sentence means.
Thanks a lot for the perfect explanation.
Everything is clear now.
