Group By with Flow Variables and NO grouping column

Hello,

I’m attempting to learn how to use the GroupBy node with flow variables. Within my process however I do not need to group on a field, I just need to get the sum of each column. I’ve attached a sample workflow demonstrating my issue.

Group By Flow Variable.knwf

I’ve configured the flow variable section as such:

But when clicking apply it says “Invalid settings: please select at least one group column or aggregation option”.

I played around with the sample workflow from this thread Using Flow Variables with GroupBy – KNIME Community Hub

I mirrored the same process except for adding a group variable. It seems like I have to manually add the aggregation columns even though they are supposed to be controlled by flow variables.

Hoping to get some help or suggestions.

Thanks, John