We do have a compound grid function in the singularity-extras plugin. This only works with overlapping uniform columns though, not non-uniform columns.
That said, $grids: 1 .382 1;
should get you what you are looking for. The golden section is pretty fun to divide things with because every part is still on the same scale making this calculation a little easier.
If you wish to write a function to make any of this easier please do. It’s as easy as writing a function that spits out a list of numbers.