Turn the Badger 2040 E-Ink display into a programmable macro keypad using CircuitPython. The firmware for the Badger 2040 keypad is a derivative of my PicoSplit firmware. You don't need to install any additional software on your computer. A simple text editor and a web browser is all you need. I provide the firmware for free under the MIT license.
The badge is held magnetically on the keypad and can be easily attached or removed, because Pogo Pins are used for the electrical connection. You can even do this while the badge is connected to the computer. The badge will then automatically switch to the appropriate mode. When plugged in, it shows the keyboard mapping of the additional keys and when operated without the external keyboard, it shows the mapping of its built-in keys.
You can find a rather detailed instruction for building the keypad on my homepage.