Following a lead, there is a way to do this. For the price of some extra effort.
Using a Rectangle (or Polygon) with terraforming, they can be sunk into the ground leaving a hole. Make the Rectangle about 13x13 meters to surround the pylon. (It can be helpful to rotate to align with the terrain to keep the final hole square.) Enable terraforming, set the falloff to 1, if needed ensure the priority is higher than any other then might interfere. Then sink the Rectangle down about 37 meters. At the surface the hole will be about 20 x 20 meters. My plan is to cover the holes with a scenery object: a concrete cap, as if the base foundation of the previous pylon was left in place.
Obviously, if the hole is on the airport grounds, the covering object should be roadmaterial to keep aircraft from falling in. Collideable is an option for certain uses.