Michael’s right. In 5.5, set your Audio Project/Output settings to Direct Out. This enables you to send audio tracks in the timeline to physical outputs of the Mojo DX. I believe with the Mojo DX it’ll give you the ability to output up to 8 individual audio channels.
From there, you need to export a QuickTime Reference file. Make sure in your export setting that you do not choose Mixdown Audio Tracks. The reference file will point to your individual tracks. From there, open the ref QT in QuickTime Pro. Do a “Save As” to a self-contained movie, and you’re done. Transcode from that file to ProRes.
This is the easiest way to get there. There are other ways, for sure, but they involve more steps and invite the possibility for error.