First of all graphic library which you use doesn't have much inpact on making game map editor woth exceptions of 2D and 3D capabilities.
Also it laregly depends on what kinda game are you trying to make.

But in short if you know how to make game it shouldn't be hard to know how to make editor. If we are talking about 2D game you only need to make yourself and aplication which provide you with the ability to chose and place certain parts of the mape (usually sprites).

Not so long ago I was helping another member with making of editor for his own planned game. We haven't finished it which might also be partially my fault. I actually lead him to wrong path on faulty asumption that something can't be done using the graphic engine he was using (I asumed that the graphic engine doesn't have any optimization) so we wasted several weaks on implementing custom optimization which only lead him to confusion. I hope I won't make same mistake again.

Any whay you can find some more infor on this here (all of our mishaps): http://www.pascalgamedevelopment.com...er-Game-Editor