DxO Optics Pro’s distortion correction is designed to produce a rectangular output, so the software typically crops away the empty edge areas created by the correction. In practice, there isn’t a normal option to preserve those undefined corners as part of the exported image.

If your goal is to do final rotation and cropping elsewhere, the usual workaround is to export with distortion correction applied and then continue editing in another program, understanding that DxO has already trimmed the frame to keep it rectangular.

In general imaging terms, those missing edge regions are not real captured image data, so once DxO has rendered a cropped rectangular result, they can’t be recovered afterward. If preserving every possible pixel around the corrected frame is critical, you’d need software that allows distortion correction without automatic crop or that can export with transparent/blank borders.