Software update: MKVToolnix 71.0.0 – Computer – Download

Furthermore @wc2wc:

With MKVToolnix ‘mux’ your files. I think it can best be described how to fill MKV files with parts like video, audio, subtitle, cover art, metadata, etc. Those parts themselves remain unchanged.

There remains 1 MKV file containing all (selectable) parts needed for viewing and archiving. If you want, you can remove those parts later or mux with other parts for a new MKV.