Will there be damage if I don't shovel the snow off (due to snow thaw/freeze/thaw)? Is it safe to use a metal shovel on vinyl decking? Is it ok to allow the stuff to melt naturally if I don't plan to walk on it?
Why do you need to get the snow off of it? Unless the mass of snow is so large that it will cause the deck to collapse, leave it there.
Shoveling a vinyl deck can do more than just scratch the vinyl. You can crack the plastic. Cold vinyl will be significantly more brittle than it is under normal conditions. Enjoy the view. That snow will melt before long.