The organizer is cut by one slot, so it only provides 7 slots per plate, but the plates are extendable like puzzle pieces (at least for the rows). It is designed so that 4 plates for hexagons and one plate for rail stacking fit exactly into the original Gravitrax box (32,5cm)
I reconstructed the rail stacker from scratch and made it modular with 3cm holes, so you can place the vertical stacker where you want.
It is available under Tinkercad: https://www.tinkercad.com/things/2gE7Y5IDdLS-gravitrax-organizer/
The author remixed this model.
made pieces modular, added rails stacker.