[Rob Wilson]

I know this thread has been inactive for a long time, but this question has been bugging me for a while, especially because of exporting an OMF from my video editor. However, I’ve found a simple & fast solution:

https://helpx.adobe.com/audition/using/clip-volume-matching-fading-mixing.html#create_a_single_audio_clip_from_multiple_clips

Basically, you make sure each mono track has their respected L100 or R100 pan, then select both clips, then go to Multitrack > Bounce To New Track > Selected Clips Only. Voila, 2 mono tracks into 1 stereo.

Cheers!