I use software that separates Discord, game and background music into virtual audio outputs. These are used as inputs for recording software, so that they can be excluded or included in the final recording.
While this works great for OBS's mixer that can create one video file with those inputs as different channels, I've noticed that Relive is a lot less intensive on system performance and would prefer to use that.
Currently the only option in Relive is to separate the microphone audio, which outputs it to an audio file alongside the video recording.
It would be great if there was an option to add more audio inputs even if they just export as separate audio files like with the microphone. Ideally for organisation if everything was combined into one video file with different audio channels like OBS that would be amazing. 
Thanks for taking your time to read.
- Jack
I have a similar problem with my ASTRO TR40 Headset. I can split it into a game and voice audio line for better control with the Mixamp but ReLive only records the default audio line and nothing else. Because of this I can't have my Discord and my game audio at the same time. I've put a screenshot below for better understanding what I mean with the two audio lines.
