Thank your fourmajor for the blog post. It was very helpful 
I was able to install the above module. However, I can’t find the “new” function. Does anyone have an idea what went wrong? The logs does not tell that any errors occurred.
Log: Starting up module ‘com.paulwurth.expressionfunctions’ v1.0.0 (b0)…
In addition, this picture shows, that it was successfully installed:
Thank you