I am not sure this option is there, I have not seen it, so here it goes: There are cases when we need to raise (or lower) the terrain altogether without losing all the work we have done. It should normally not happen but it does, and in this case one has either the option to redo the entire terrain, or export the height map and modify it externally. All this would not be necessary if we could with a single click offset the height of the terrain height up or down to the amount we need. It does not need to be precise, as long as it is a single click process and we can by using small values even with decimals and repeating the process to fine tune it to perfection. It would still be a lot faster than the other options and save a lot of production time.