This topic comes up from time to time, so here are the instructions for adding Apple-style M4V/MP4 markers to Vegas renders. These will work with most players such as VLC. Don't confuse with other types of chapters -- DVD chapters are a whole different critter.

-- Download freeware Drax from https://www.videohelp.com/software/Drax

• IN VEGAS:

1) Render your file (using Sony or Magix AVC), and rename the .mp4 extension to .m4v (important).
2) Open the Vegas project you used to render your file, make sure to set your Time Format to "Time", and check View->Show Edit Details.
3) Choose Markers / All Fields.
4) Click the upper left box to select the whole table. Ctrl->C to copy the marker data.
5) Open a new Text file on your desktop. Paste the marker data into the file. Save the file.

• IN DRAX:

1) Open your renamed .m4v file.
2) Click on the "Chapters" tab at the bottom of the window.
3) Go to File->Import Chapters
4) Click on your newly-created chapters.txt file (you can also edit or add chapters manually if wanted).
5) When the new chapters have imported successfully, click File->Save.

That's it! Works with any AVC MP4 file with an .m4v extension, not just iPod / iPhone. Works with Handbrake files.
Drax is a very simple, intuitive .mp4 /.m4v tag and metadata editor. Does it well.

This is a repost from 12 years ago, so if you run into any problems in VP20, let me know.