Hello Nicolas
Yes, it was the file I needed but unfortunately my knowledge and skills of PHP is not sufficient enough to get the field visible where I want it.
I solved it with a workaround:
Since I only needed a handful different texts I put these in custom modules.
> With Regular Labs' "Advanced Module Manager" I assigned these to the user groups.
> with {loadmoduleid …} I show the modules in the description field of the product.
This works even better as I cab have an image in the module as well.
Thanks for your time