I’ve got those microwave rubber mats that Nankate and others mentioned, bought years ago from Lakeland and forgotten about in a drawer! I dug them out again recently, when the energy prices went sky high. Before that, I was merrily turning the oven on for 10 minutes or so if it wasn’t already on to warm them, then saw on the smart meter monitor how much power that was using.
But if I put anything to warm in the microwave, the plate is cold enough to lift it out without an oven glove. I don’t warm plates in the microwave because the instructions say not to, but do they actually get warm enough (assuming you like your plates warm) if you do?