You don’t need to combine anything, it is what ScaleSpaceDetector does. https://kornia.readthedocs.io/en/latest/feature.html#kornia.feature.ScaleSpaceDetector 2
Look at this example: https://github.com/kornia/kornia-examples/blob/master/image-matching-example.ipynb 10
and instead of resp = BlobHessian() use resp = BlobDoG() and pass scale_space_response=True when creating ScaleSpaceDetector