The above printer was only driving 2 stepper motors per axis and so in the above picture there is 1 signal getting split to 2 stepper drivers and then each going to it's own motor. I later corrected this wasteful setup and just ran splitters with TMC2226 drivers. But if I needed to drive 4 motors in the same way I would put both of these setups together and split both sides of the stepper signal. In the below picture I have 6 motors driving movement on my printer and a 5 filament Prusa MMU2S and if you look on the SKR 1.4 Turbo there is still an open socket for another stepper..