Get Component in C++

Usually you will add it as a property. In header:

UPROPERTY(VisibleDefaultsOnly, BlueprintReadWrite)
	USceneComponent* DefaultSceneRoot;

And create it in class constructor:

// Default root
DefaultSceneRoot = CreateDefaultSubobject<USceneComponent>(TEXT("DefaultSceneRoot"));
RootComponent = DefaultSceneRoot;
DefaultSceneRoot->Mobility = EComponentMobility::Static;
DefaultSceneRoot->bVisualizeComponent = true;