qmk_firmware/keyboards/zj68/keymaps/splitbs
..
keymap.c
readme.md

ZJ68 W/ Split Backspace

The plate that comes with the kit from Drop only allows one layout, but the pcb supports having a split backspace, so by widening the plate where the stabilizers are meant to go, you can fit the two switches in, if you want to go back to a single backspace later, you can still use pcb mount stabilizers.