Is the fourth character called the Quadragonist in a film storyline novel etc?

Although you could expand the greek Wording that far, it wasn't ever done by the Greeks. Ancient Greek drama involved only three actors (the protagonist, deuteragonist, and tritagonist) plus the chorus, with each actor playing several parts if more were required.

• The main character is called the Protagonist
• The second character is called the Deuteragonist
• The third character is called the Tritagonist
• The villain is called the Antagonist

The fourth character could be called the Quadragonist, but this was never done anciently, and is rarely done in the modern day.