In other languages the equivalent would be an array of arrays of arrays.

It would be slightly unusual to require such a structure, but if that problem required you to do that, that so be it. I can't imagine anyone calling your abilities into question if you did that in Java or Python.

Haven't used C for decades but I'm sure we used to do things like pointers to to pointers to functions that returned pointers to pointers. When you've got 16KB of memory, a 2MHz processor, and a poorly optimised compiler, you can't worry too much about readability.