10 hours of search and code for that. It was worth it, right? Right?
Now I don't have to : right-click > english audio and right-click > french subtitle. It launches every video of the season ready to go. It was worth it, right?
Now it's time to enjoy my day. Oh wait! (it's 6 am here)
That's what I already did. And finding the good mkvpropedit command was long.
But here I wanted to automate that and just having to choose the audio and subtitles languages and it executes the mkvpropedit command.
I'm not sure if it's fixed now but a few years ago Plex ignored the properties and played the first audio stream it found. I had Scooby Doo with Portuguese as the first audio track and although mkvpropedit worked when playing back in VLC, in Plex it would still play Portuguese as default. I had to re merge the streams with English as the first track for Plex to play English by default.
Either your file had the propertie flag --forced-display-flag for the audio track 1 and this would force the audio 1 to play even if you changed the flag-default with mkvpropedit. In that case you have no other choice to remux your file with mkvmerge and change the flag to --forced-display-flag 1:no (if it's the audio track 1) I have no idea why someome would force an audio track....
Or you didn't used the --edit track:s1 flag with the flag-default propertie, which uses mkvmerge under the hood. Reading through my notes there is a superuser.com link talking specifically about that, and how it could fuck up your tracks order if you don't use the track flag.
Edit: This is only true if your player is capable to select the audio based on the flag default or forced. Otherwise you have to remux the file and change the order of tracks with the --track-order flag with mkvmerge. This could be the case for Plex, you can probably find that info in the plex documentation !
Edit2: Plex seems to use both but I would suspect plex or bad flags being the culprit here rather than mkvtools.