[Closed] Creating custom field grids?

In the Viewport Configuration, under the Safe Frames tab, you can enable the 12-Field Grid either as a 4×3 or 12×9 setup. I was wondering if it is possible to make custom field grids, namely a 3×1 setup to achieve the “law of thirds” composition technique.

If anyone has any scripting ideas for this problem, it would be great.

Thanks.