SUMMARY Vlc has this option and mpv supports it as well, would be nice to have an option for it in the menu under audio > track OBSERVED RESULT no way to add external audio file to a video, not even using the command line woth mpv flags EXPECTED RESULT a user friendly way to do it
If I remember well, MPC-HC (available for Widndows only, but open source) also had it: https://github.com/clsid2/mpc-hc I used it with a few external audio tracks (other languages dubbings). Anyway, until this is added, anyone who really needs an external audio track, if the container is Matroska (.mkv), the track can be muxed in with MKVToolnix and then it will be seen by Haruna too.
> if the container is Matroska (.mkv), MKVToolnix can read basically everything. The input format isn't limited to mkv.