How to configure new Joiner Node using flow variables for matching criteria

Hi there,

I am running Knime 5.3.1 version, most of the time under classic UI.

I have multiple table that I would like to join into a Table Row to variable loop start.

So I would like to dynamically setup the join columns.

I have tried to manage a Flow variable for both Left & Right table as a List.

But when I get into “Configure Flow variable” , i can’t choose such type of Flow Variable. Only option is a single string. See the capture below :

But, it is possible in the "SelectionConfig as illustrated below.

In my remember, in old version it was possible to specify variable List into LeftPredicate or RightPredicate.

Did I miss something ?

Is there a different way to do the same ?

Many thanks in advance for all the help you can bring.