Can I use a variable AC transformer to adjust the output of a radiant heater?
I wouldn't mess with stuff like you are proposing. Electrical resistance heating always requires a lot of power. There's too much junk out there to be sure it's safe to use with a constant load like an electric heater. Like Harp has &quot;harped on&quot; (pun intended) often is stuff sold on Amazon often doesn't meet UL listing and other USA safety testing. There are a number of good alternatives to the setup you are proposing, like under desk warming panels that are safe.   Do some research, but don't try to power down a heater like you asked, it's asking for trouble and potential fire.