Hello,
here is a modular rack system for a Gridfinity box i found on Printables. https://www.printables.com/de/model/495142-rugged-gridfinity-box-parametric
The Rack is made for the 4x4x6 variant of the box.
Per stack you need one bottom part and as many modul parts as you have boxes.
The moduls are held together by 4 M3x12 Hex head screws witch are self tapped into the print.
Material is Bambulab PLA-CF but feel free to print in any material you wish.
No supports needed.