Well thank you again for this detailed anwer. I will add more comment in the future. The magic numbers you mentioned is a function that returns an Array (in Dart: list) of possible video qualities. This happens with checking whether the desired quality exists in json_metadata.
Wrapping lines can be done, though Dart especially Flutter is known for those heavy indents. But its true I could have avoided a few of these.
Some of the unused parts are important and some not. Will sort this out.