If one has a pot of soup on the blech a little further away from the fire may one put it on top of a pot that is on the blech closer to the fire so that it should warm up more?
Thank you for your question.
Moving a pot is soup closer to the fire, depends where the pot is when it is moved. If the pot of soup is fully cooked and it was in a place that the fire will keep it yad soledes bo, it is permitted to move it closer to the fire even if it isn’t on top of another pot. However, if the soup is not fully cooked, or if it is in a place that the fire will not keep it yad soledes bo, then it may not moved, even on top of another pot, if than place will make it yad soledes bo.
Igros Moshe O:CH 4-61, Shvus Yitzchok Shiya chap. 6.