Multiple audio tracks

Hi! I record games and I use MP4 (AVC/AAC) with 3 audio tracks. Not channels, tracks. I'm using Media Encoder to make low quality versions of my recordings. But I can't find an option to keep the 3 audio tracks in the output file. The only option is 5.1 audio, but it creates a single track mixing the 3 tracks (wut?), and I don't want that. Is there a way to keep the 3 tracks? Thank you! BTW, when selecting 2 channel audio (stereo) it creates a video with only the first audio track of the original file. These things don't make any sense.