Thanks @tiffle for your answer, unfortunately I did not have the chance to look at your answer in detail before it was deleted again.
I have not found a real solution, rather a workaround that helps me in my specific case. Therefore I close the post here, thank you for your attention.
Hi @micha_ontour, thanks for the response. My original post didn’t solve your problem unfortunately but I do have a Keyboard Maestro-based solution that I can share with you once I get back to my desk later today.
The macro that does the copying and which calls the utility subroutine.
The utility subroutine produces a list of all the files contained in a folder and all its sub-folders recursively. It does this by making use of the macOS shell command find.
In this macro you need to change the values of the source and target folders in the actions (1) and (2) while action (3) is the actual call to the above subroutine.
I've tested this on my system (KM v10, macOS 10.14.6) but as with anything that involves copying files, you should test this first on your system to ensure it does what you wish.