VLC is a good player, but it can happen that if you create only one mkv chapter, it doesn’t recognize it (unlike other player such as, in Linux, SMPlayer).
To fix this you have to add at least two chapters,
how split a mkv with subtitles
You can use mkvtoolnix, then go to -> output, and -> splitting -> by parts based on timestamps -> and there you can write the beginning and the end of the part you want extract (without spaces: like 1:02:07-1:04:40, for example).
problema muxando un file mkv (e aggiungendo un file di capitoli (xml))
Possibile errore: “The XML chapter file ‘nomedelfile.xml’ contains an error: ” is not a valid ccTLD country code.”
Soluzione: aggiungere, editando il file dei capitoli una “country”.