Tag/Events with Variables


I am trying to setup a Matomo Event using as Event Action the Value of a Variable.
The Variable seems to be correctly defined, as in the Debug mode the Variable works, but in the Event instead of the Value of the Variable a string is passed with the name of the Variable. As Example {{Variable}}}} . with 4 closing brackets (!!)

I tried to define the Variable in different ways, same result.
I have tried to define Event with the predefined “Matomo Analytics Tag” and also to geneate it with HTML _paq.push() … same result.
Any tip what I am doing wrong?

Thanks in advance,