There's not, but it's a good idea. Map expansion works by cloning a row/column, so currently the best option is to clone the first row/or column and then edit it down. Obviously that's a bit of a headache if you've got a lot of editing already done on that first row and need to terraform. I've also got a todo to make the map rotation controls work against the visual center (right now it pivots around the center of the base 8x8 map, which is pure oversight on my part).