Assuming your audio files are BWF files, you could use the helper application that comes with my AUX TC reader:
Donwload the package, you need the BWFQTmerge application:
https://www.videotoolshed.com/product/26/fcp-auxtc-reader
What it does is finding matching TC, and paste the BWF into the QT, either self contained or by ref.
Two warnings:
The video duration will be important. QT does not allow the audio to start before the video, but the other way around is no problem.
Do NOT use dual mono in combination with Poly BWF files.
If you do so, things will work, but you will NOT be able to media manage the files.
The correct way to work if you have a mix is to either remove the original sound (using my free QTchange application), or alter the BWF to match the sounddtracks. (Most of the time that means splitting the poly files into mono files)
hth,
Bouke
https://www.videotoolshed.com/
smart tools for video pro’s