My keyboardio came i tried various ways to get Neo working. But for some weird reason in the hid spec I can not send utf-8 codepoints but quite obscure things for videorecorder or alarmclocks.
So I took the trusted way of the neo auto hot key helper (http://neo-layout.org/neo20.exe) and can now use all 6 layers of neo.
The changes to the default keymap are rather small. The biggest changes were for the compose keys.
The default function layer from keyboardio preserved on the left of the neo U.
The numpad is gone because neo has already one on layer 4.
[QWERTY] = KEYMAP_STACKED (___, Key_1, Key_2, Key_3, Key_4, Key_5, Key_LEDEffectNext, Key_Backtick, Key_Q, Key_W, Key_E, Key_R, Key_T, Key_Tab, ShiftToLayer(FUNCTION), Key_A, Key_S, Key_D, Key_F, Key_G, Key_Equals, Key_Z, Key_X, Key_C, Key_V, Key_B, Key_Escape, Key_LeftControl, Key_Backspace, Key_Spacebar, Key_LeftShift, Key_CapsLock, M(MACRO_ANY), Key_6, Key_7, Key_8, Key_9, Key_0, Key_Minus, Key_Enter, Key_Y, Key_U, Key_I, Key_O, Key_P, Key_LeftBracket, Key_H, Key_J, Key_K, Key_L, Key_Semicolon, Key_Quote, Key_RightAlt, Key_N, Key_M, Key_Comma, Key_Period, Key_Slash, Key_RightBracket, Key_RightShift, Key_LAlt, Key_Spacebar, Key_RightControl, Key_RAlt)
edit Forgot about alt + tab now its restored.