Syntax for database variable 'custom_var_v2' in the tracking code?


I am trying now for several days to show the value of the variable “Loggeduser” in the visitor log.
I tried with the nfrPiwik plugin for Joomla and with the jpiwik plugin for Joomla.
As third alternative I could edit the database entry for the tracking code in the Joomla database itself.

But I can not find out, how to insert the following in the tracking code:

I only want the Piwik database variables ‘custom_var_k2’ and ‘custom_var_v2’ from the database table ‘piwik_log_link_visit_action’ to be shown in the visitor log.

I tried to simply enter “custom_var_k2” and “custom_var_v2” in the “administration”, “web sites”, “get tracking code” field for custom variables. That creates this line in the tracking code:

“_paq.push([“setCustomVariable”, 1, “custom_var_k2”, “custom_var_v2”, “visit”]);\r\n”

But that only shows just these entries as label and as value in the “visitor log”: custom_var_k2: custom_var_v2.

That is of course not, what I want. What is the correct syntax for the tracking code to show
the label 'piwik_log_link_visit_action.custom_var_k2’
and the value ‘piwik_log_link_visit_action.custom_var_v2’ in the “visitor log” ?

I would not spend so many time with trying out, if it would not be so urgent! Tracking is needed for the evaluation of a training study for patients with Multiple Sclerosis and the study is already productive.

Due to this, THANK anybody for any tipp!