Is it safe to use a 10 ft non-UL listed power cord for my dryer
You can make a cord using listed components. A 10awg 3 with ground SO cord (4 wires) and the correct cord cap you can make the length you need and it would be legal. a link to the wire and the plug  (normally called a cord cap). I would use crimp connectors on the end that attaches to the dryer because the SO is fine braided wire like this. Here is a link to a cord cap not sure if it is the same as you have but it will give you an idea if you were not sure what I described cord cap link.