It happens that I have a AVCHD stream with stereo signal that is actually two separate mono channels. What is The MEPP way of muting one and use the other as a mono signal (or as in my 5.1 vision, assign one stream to the center speaker, the other one to the rear speakers)?
Double-click on the audio object to open the Audio cleaning interface, select Stereo FX tab, open the pop-down beside preset and select the one that you want, like "both channels = left."