Accented characters on a modified AZERTY keyboard

I have an AZERTY Belgian keyboard on my Macbook Pro 13" running Sierra 10.12.6 and installed a modified Belgian AZERTY keyboard layout ( Ukelele app) only inverting the 0 to 9 keys (numeric keys) so that I do not have to press shift to insert numbers. The new keyboard layout is installed in /Library/Keyboard Layouts so that it can be used by all users. I added the new keyboard layout under keyboard preferences, others.

From that time the new keyboard layout could be selected in Safari, but not in any other application such as Pages, Texteditor, Agenda ... etc. The "key holddown" function for special characters did work as with the standard keyboard in Safari.

After restart of the OS all other applications were able to select the new keyboard layout, but the "key holddown" function stopt working only for the new keyboard layout, and is still available for the standard keyboard.

I was not able to get a reading of the ApplePressAndHoldEnabeled setting with the "Defaults read -g "command, it returned "domain/default pair" not existent.

So is this setting still available in 10.12.6 or are there settings per keyboard layout that would explain this.