Programming a layout in Arduino (Teensy 3.1)

[possumgumbo]

I am attempting to program this layout: http://www.keyboard-layout-editor.com/#/layouts/41278b39d92833e044007ab46bb8a9f8
in Arduino using the keyboard or keypad library.
Is there a guide for this?

I have built the keyboard, but have not figured out how to program it. I have looked at the https://github.com/kiibohd/controller,
but I highly dislike the complicated methods for loading the program; I bought a Teensy so I could use Teensyduino.

Has anyone ever made a keyboard actually using the Teensyduino methods described on https://www.pjrc.com/teensy/td_keyboard.html?


Other notes:
When held, the DEU key adds umlauts to vowels and changes S to Eszett.
When pressed, CHAR MAP brings up the character map (WIN key, send 'char,' send 'enter')
Num lock switches the right side of the keyboard to a numpad.