
- Open 'MKVToolNix GUI'

- Drag 'Tenet (2020).mkv' (or, whatever you called it) into 'MKVToolNix GUI'

- Refer to 'Tenet.2020.1 (Small).jpg'. IF there is a 'Chapters' entry in the 
  'Track' listing, there is nothing more to do.
  
- IF NO 'Chapters', refer to 'Tenet.2020.2 (Small).jpg'. Browse to where you
  extracted e archive & select 'Tenet.2020.UHD.chapters.txt'.
  
- Select 'Start Multiplexing' as noted in 'Tenet.2020.1 (Small).jpg'.