All nodes are based out of UK2Node class (K2 = Kismet 2 as blueprint is evolution of Kismet from UE3) so you can find it here: Source/Editor/BlueprintGraph/Private/K2Node_MakeMap.cpp
All nodes are based out of UK2Node class (K2 = Kismet 2 as blueprint is evolution of Kismet from UE3) so you can find it here: Source/Editor/BlueprintGraph/Private/K2Node_MakeMap.cpp