Here is an almost finished design, all it needs it a little tweaking of the bottom silkscreen. Time to add a USB label indicating which way the Arduino Nano is supposed to go.
The footprint for the Nano has been placed with the USB connector facing towards the LED displays. While this design will technically work, the USB port is concealed.
Time for a quick re-design:
Now the USB connector is facing left. Notice the location of the VIN pin, fed from the power switch. The cost of this redesign was two more horizontal traces in the front to get power to the right location now that is away from the power switch.
Witness the importance of double checking wiring. The menu key (above the 0, is wired to the same select/return line combination as the 0 key (bottom of image). Luckily, another return line passes by and is just a matter of switching the bottom of the pushbutton to a different return line.
By simply connecting the bottom of the key to another return line, the menu key now has a unique select/return line combination.
Since these circuits are wired without using a schematic, very careful checking is needed at the end to make sure everything is wired correctly.