Answer by Ochreous

I found a way to make it work. You just change the SetQualityLevel's integer to overallQualityInt. int overallQualityInt = GUILayout.HorizontalSlider(overallQualityInt, 0, 4,GUILayout.Width(150), GUILayout.Height(35); QualitySettings.SetQualityLevel(overallQualityInt);