This Gridfinity filament storage solution has two 1x5x6U “bins” connected to each other with rods. Two bins are placed 4 grid units apart (e.g., a single storage unit spans 6 grid units including the bins). Each bin can hold rods in two directions, so these can be extended as much as you want.

Rods connect to the bins with small hexagonal dowels.

 The bins have a stacking lip, so you can either place ordinary Gridfinity storage bins on top, or use some empty bins (I printed a few Gridfinity lite bins 1x5x12U) to stack even more Gridfinity on top!

This is probably a huge waste of plastic, but I rather design this than order wooden rods or god forbid, leave my house. Enjoy :)