It seems that I can set transform to the vtkCamera. And I tested with VTK 9.0.1 it works.
vtkNew<vtkTransform> transform;
transform->Scale(2, 1, 1);
renderer->GetActiveCamera()->SetModelTransformMatrix(transform->GetMatrix());
Though there are some problems that is connected with vtkCubeAxesActor
.
P.S. as I have previously created topic dedicated to adding vtkCubeAxesActor to the Slicer’s scene, I think I should discuss the mentionned problem there.