CH57x Keyboard Mapper
Designed for the programmable macro keyboards from online stores and is an open-source alternative to the software offered by the sellers. Maps keycodes and macros to keys on the original firmware.
Standard keys follow USB HID keycodes but modifiers, media keys, and mouse buttons seem to follow a different format. The original software offers programmable layers but there seems to be no way to access the non-default layer (no functional FN keycode).
Tested specifically with the 12-key + 2 rotary encoder model running a WCH CH57x chip. Untested for other similar models. Currently hardcoded to search for the specific vendor and product ID of the tested model.