Modular swappable
Found some cheap 6 position shunt jumpers at Allelectronics.com. These are a fraction of the cost of new. Used these on a set of 4x4x4x4x4 PCBs. Only needed a 4 position jumper, but these fit fine and are really cheap.The four assembled PCBs separated.
Bottom view of the 4 PCBs. Jumpers are installed on one side of each PCB. The header pins were the ones that came with Pro Micro clones. I snapped each 12 position pin into three 4 pin sections.
Close up of the pins and jumpers.
The 6 position shunt jumpers.
Side view of the installed jumpers.
All 4 PCBs connected.
Side view. The jumpers make good electrical connections but do not physically hold the pieces together well. A bottom plate is necessary.