I wanted a way to stack multiples of PeterDesigns (over on Printables) gridfinity cases and get to any of them without having to move all the cases on top of the one I wanted so I made this. It's designed to hold 6U in a 6x5 configuration. There's left and right brackets and three different spacer bars. The thinnest goes on the top and bottom shelf, the thickest one goes between shelves, and the middle thickness one goes on the back side. There's holes on the side brackets so you can attach it to some 2020 extrusion so that it can be lifted off your worksurface and attach multiple stacks together.

After printing a few racks, I've noticed that the spacer bars are just a touch too short, depending on what filament you use you might have very snug cases so I've made them 2mm longer just to give a little wiggle room.

The print profile has these longer bars now, and I've added a separate profile with just the bars. I also have added a new 12u tall version in case you have double height cases.
 

Here's a link to the case on printables. Rugged Gridfinity Box (Parametric) by PeterDesigns | Download free STL model | Printables.com