Need custom variable "LoggedUser" in the visitor log

Hi there,

Piwik shall be used for a closed wikipedia system, that is only for training and education. We must see, which users use the wikipedia, and how often. For that we need to see the username.
I have activated the “LoggedUser” as custom variable.
In the visitor log only the IP number is shown. In the custom variables I can see the username (LoggedUser).

In the UserGuide chapter “Custom Variables Analytics” is shown, that custom variables should appear in the visitor log. But that does not happen in my Piwik (see screenshots attached). What is wrong? What shall I do to see the username in the visitor log?

Thanks very much for any tipp!