I made the Stream Cheap (Mini Macro Keyboard) made by DaveM on thingiverse which emulates the unused F13-F24 keys. But the code wasn't made for simulationg keycombination presses (like shift+F1 and such and the games/programs I wanted to use it with don't support F13-F24), so I made some changes to the code to make it work like I want to and easier to change the keyoutputs.
The code is made for the Arduino Pro Micro 5V board with HID support.
THIS IS A WORK IN PROGRESS AND I'M STILL TRYING THE CODE OUT, SO USE AT YOUR OWN RISK!
(the code might change so it can be good to keep an eye here for updates)
Link to the original creator with instructions and the .STL files for printing the case:
https://www.thingiverse.com/thing:2822140
https://www.partsnotincluded.com/electronics/diy-stream-deck-mini-macro-keyboard/