Create a custom QualityLevel

Hi guys, I just want to be sure of it but :

is it still unpossible to edit the QualitySetting class or do anything, in order to create a custom QualityLevel and be able to change dynamically variables like Anti-Aliasing, Shadow Resolution, or Texture Quality?

and if the answer is yes : isn't it possible to create a script that would do it the same way Unity do ? (actually I'm pretty sure it is, but I'd like to know if someone already wrote something that way)

You could always edit them to create custom quality levels. Just go to the quality settings in the editor and change whatever you like.