auto name = this->GetName();
name += FString("-wall");
_instances = CreateDefaultSubobject<UInstancedStaticMeshComponent>(*name);
After adding component Wall to Actor in editor I can see that InstancedStaticMeshComponent was attached to Actor and I can edit it using blueprints.
BUT in Details window of attached Wall, there is editable property **Instances **(of type InstancedStaticMeshComponent), which seems to be different one than the attached component.