This is great yawor !
I can exactly do what I want thank you again for all details, explanation and research ;)
I was very far from find that way of USB HID !
Now, I check the HID of the key convert it and record it.
For example if I want LEFT WIN + LEFT CTRL + r:
MODIFIER_VALUE = LEFT WIN + LEFT CTRL is 8 + 1 = 9
HID_KEY = I check USB HID for 'r' is 15
KEYCODE = convert the hexa in decimal give me 21 (http://www.binaryhexconverter.com/hex-to-decimal-converter)
Record my key:
./flirc_util record_api 9 21
For GNU/Linux users you can directly search HID and use:
./flirc_util record_api 9 $(echo "ibase=16; 15" | bc)
./flirc_util record_api MODIFIER_VALUE $(echo "ibase=16; HID_KEY" | bc)
It's work like a charm on GNU Linux of course ^^