Hi Salkerx777, thanks for your reply.
I just checked your hda and it seems to have what i'm missing, nevertheless when i try to launch the ui there is this error (see attachment)
From my side I find a "solution", i can get the content of the ui with hou.readFile(opdef....), then write this content on the desktop in a ui file and pointing on it when launching, then deleting after the ui.show() (so it's transparent for the user)
But your solution is more convenient^^, and i'm very interesting to work with it