I added a second spiral (making it a double helix) to BouncyMonkey's Yet Another Dice Tower. This allows for dice storage in the void left in the original design. Using a spring in the top, you can lift and spin it 180° to select which staircase to use.
Only way to empty the storage side of the tower in this version (I have ideas for a future design...) is to turn the tower upside-down and pour all the dice out. Fun but they do like to go everywhere.

Had to learn some Blender skills to mod the original STLs, thanks to my OH for showing me how to do that. Most of the other changes made in OpenSCAD.

Required Minerals:
M5 threaded rod (length as required)
M5 locking nut (x1)
M5 thin nut (x3)
M5 washers (x3)
Spring ~10mm long and >5mm diameter
large fizzy pop bottle
glue

Thanks to:
BouncyMonkey's Yet Another Dice Tower
GrooveDachschund's Another Dice Tower V2