Download and install MKVToolNix, then use the GUI to add your media files, select desired tracks, and choose output settings via the main interface.

Yes, use the 'Multiplexer' tool to multiplex video, audio, and subtitle tracks into a single MKV container easily.

Open the 'Info' tool, load your MKV file, and explore element-by-element details, including tracks, chapters, and attachments.

Use the 'Chapter Editor' to load your file, modify chapter points, and save the changes directly within the application.

Open the 'Header Editor', load your file, select the track or attachment, make edits, and save; access via the main menu under 'Header Editor'.

Use the command-line tools or the job queue feature in MKVToolNix to set up automated, background multiplexing workflows.

MKVToolNix is open source and free to use, but purchasing through the store supports ongoing development and provides automatic updates.

Visit https://mkvtoolnix.download/ and purchase directly; support benefits include automatic updates and development support.

Purchases support updates and the development team; MKVToolNix remains fully functional without payment but support enhances features and updates.

Check your input files and settings, update to the latest version, and consult the user manual or support resources for troubleshooting tips.