I am using Mac OS Mojave. OoKushoO at first I too did not have any WAV file, and I was stuck for a long time. Don’t give up! Look, I see what you’ve done incorrect. You wrote -audiomixer in the wrong place. First scroll till you see and check the box that says “Use separate process.” At that point add -audiomixer in the additional command line argument box and the inherited command line argument box. Make sure you name the file where it says Audio file name, and give an output folder for the video in general. Good luck! I hope you make it :).