73
Max
I built mine on just a T4.0+SGTL5000 and back then each keyer app tested back then (TeensyWinKeyEmultor, Hasak, Prototype, K3NG) each of the keyer versions had slightly different code usages.
Some discussion about this is here: CWKeyerShield Library · softerhardware/CWKeyer · Discussion #19 (github.com)
Most of the SDR apps have a MIDI configure and test page. IF you have a keyer running, you can operate each knob, switch and keyer input and see what code(s) is produced and assign them as you see fit.
This file and other similar header files lists their MIDI note assignments: CWKeyer/software/cwkeyer/cwkeyer.py at main · softerhardware/CWKeyer (github.com)