[FEATURE] Split Audio Tracks
I am fairly certain that neither Hitfilm Express not Pro can take one audio track, and split it into two tracks, making one track the right audio channel, and the other the left. Maybe you could just right-click on the audio layer you want to separate, and click Separate channels. Here is a video from Gerald Undone that explains one time that this feature would be useful: https://youtu.be/cft4tg7RnfA?t=438. He uses the splitter function to make 2 tracks, one for each mic.