For those who are impaitient and want a quick workaround, or need a quick grid visible in the document itself. The file below contains a procedural texture filter. Copy / paste it into your document as top layer. You can select the grid in the input parameters (x and y, color and brightness of grid). Unfortunately, grid is only optically and does not snap. No suitable when zoomed out (at least 1px lines must be visible).   Further extensions are possible (e.g. shift star