"Allow duplicate values" for workflow variables

When specifying how to input workflow variables in order to generate reports, there is an option "Allow duplicate values", which enables to select several items in a list box. What is the behavior of KNIME workflow in this case? So far, there were only 3 types of workflow variables: string, int or double... 

Currently you can only select one item at a time, for a given variable. We have this feature including array (list) support for workflow variables on out list, but can't tell excatly when this going to be available in KNIME.