Get the ids of the tracks with mkvinfo <file name>
e.g.:
video 0
audio_disliked 1 (default)
audio_liked 2
subtitles_disliked 3 (default)
subtitles_liked 4
On windows cmd, on the folder of the files:
mkdir DEMUXED
for /f "delims=" %a in ('dir /b *.mkv') do mkvmerge -o "DEMUXED/%a" --video-tracks 0 --audio-tracks 2 --subtitle-tracks 4 --default-track 2 --default-track 4 "%a"