A PCB "bus bar" to allow three ultim8x8 modules to be connected easily. Mouse bites allow it to be snapped off easily. With some imagination, can be used to expand to larger matrices.
The first panel can be populated with a Feather M0. There are six SMD switches connected to A0 through A5 on the Feather M0, with pull up resistors (SMD 0805). Switch functions can be arbitrarily assigned in code.