•To generate a master, select the edit session coming from Snippet, Snippet+ or Multitrack and click on the "Generate a master" function 
located at the right side of the Browser.
You can also do a right click on the selected item. The "Generate a Master" function is displayed as well.
Attention : Do not masterize items coming from the "Production" tool, otherwise you will loose all information that you have put on the sound. Moreover, it is not possible to transform an original item directly into a master.