Does this support adding downmixed audio?

[eric10k93]

I just found out about this software and am trying to understand if it supports adding additional audio tracks to a file. I understand the benefit of this tool is to avoid needing to transcode... often, my problem with transcoding is the audio. If possible, I'd like to convert any files that contain only 7.1 audio. I'd like to downmix these to include 5.1 and stereo, and then Plex could just choose the best option depending on the player. Is this something that this tool can currently accomplish?