Great thread, Gérald. I think this is a good idea to help you pursue completing tutorials with English subtitles. I believe this one qualifies as it is a good instructional video.

marble:

As wimvdb stated, use the material zone selections in the vertices selection tab (shortcut "T"), select what you don't want to move, and then press the button "Fixed Vertices".

In DAZ Studio you can use the Polygon Selection tools, and create material zones if needed, or if you want to create zones specific for your draping vision. Lots of work-flow options.