Place it right after the on-screen complaint in your edit, as the response beat, then follow it with Eww Brother Eww for a second reaction. For a longer chain, end the sequence with Nelson's Ha-Ha! to close on the group laughing at the whiner.
Über diesen Sound
This clip is a short vocal sound of someone stretching out a high, whiny nii niii in a sing-song way, lasting just over a second. It feels silly and mocking rather than angry, like a childish copy of someone complaining. That playful, annoying edge makes it land as a light joke instead of a real insult.