Hi,
where would you want to see comma as the decimal separator? At this stage KNIME internally uses . as the decimal separator. So tables that you will look at inside of KNIME will show .. There is a related discussion here: Change standard decimal seperator. There is always a work-around of looping suggested by @HansS: loop over columns, convert numbers into strings and replace the dot with a comma in the string. But this will be slow for a large number of columns and you won’t be able to do math operations on the resulting strings.
Cheers,
Misha