Wet kugel? Kugel is a dovor yovesh.
-1
it's dovor losh if it's lukshen kugel from the fridge on Shabbos. It's bishul if it's cold from fridge and then reaches 180+ degrees on a commercial hot plate. Also:
+1. What is the question
As my father told me he heard from r' belsky technically you are allowed to put food on top of the cholent however there is almost always an issue (cooking some liquid)
one can only do place on top of the cholent because it's shinui/not the intention of the pot.
However if the purpose of the commercially bought warming tray is on a timer to turn on at 9am in order to heat up something cold and wet to over 200 degrees on Shabbos, then that's a Halachic bishul issue...