How to edit  DVD video file cheaply (why is it so painful?):

Use Handbrake to Convert DVD to MP4

In pre-Windows 10 — we had Windows Movie maker — Use Windows Movie Maker to cut MP4 and save as WMV.

In Windows 10 — we have Microsoft Photos — cut the MP4 and save as M4V.

Use DVD Authoring Tool to convert WMV to DVD.