WOW! I really can’t thank you enough for this @johnny-bit ! It perfectly works 
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Now I have two example scripts for creating a grid and I think it will be easier now for me if I want to create another custom guides (i found and look at the code for built-in guides in the repository, but still not sure which function to call). The golden ratio is not really important, I can guess it visually or by looking at another point, it just a “nice to have” feature.
Thank you once again!
I’ve already created the PNG based image for the aspect ratio i often used, as i used it in another software too, but thank you nevertheless, those included variation will come in handy 
Just a question though, is PNG can be used in dt’s watermarks?