I had a similar situation where a longer video (~10 min) split into two, but the audio is still a single file. I have both videos downloaded, and I'm trying to manually mix, but it is not automatically combining the two video files together. Is there something I am missing? Also, can you give some more detail onto how to export the videos and single files to my PC to mix?
If you download all of the segments to Myk storage, then manually mix the first segment, Myk should automatically recognize the remaining segments (chapters) and combine to a single video. Sometimes the files can be too large for a phone to process, so you can always export the videos and single audio file to your PC for mixing.