Mover 2.0 C++ Issue, can't found a parent class "SmoothWalkingMode"

Hello guys, I was tyring to build a Mover 2.0 system form my character using C++, but i noticed that I can just inherit the “SmoothWalkingMode” from blueprint, can’t atually found that C++ to inherit when creating a new C++ class. If i force it inherit from “SmoothWalkingMode’“ by changin the code:
UCLASS(Blueprintable, BlueprintType)
class Project_API UProjectMovementMode : public UWalkingMode
{
GENERATED_BODY()
}

to

UCLASS(Blueprintable, BlueprintType)
class Project_API UProjectMovementMode : public USmoothWalkingMode
{
GENERATED_BODY()
}
it would say can’t open the generate file, is this because the Mover 2.0 still an experimental plugin?