Easiest way to convert multiple columns to duration

Hello,

I am trying to convert multiple normal duration columns (“01:23:45”) to KNIME duration columns (“PT1H12m45s”). What is the easiest way to do it?

A solution working for one column is: split values by “:” to columns xArr[0] … xArr[2], combine them with string manipulation node to the desired format and then convert with string to duration node. I tried to make a loop based on the same workflow by using a Column list loop start node, in which I define the columns I want to convert. But I couldn’t find a solution how to tell in string manipulation node the column names. String manipulation doesn’t recognize for example: ${string($${ScurrentColumnName}$$+“_Arr[0]”)}$ or similar. I couldn’t find any reference guide for the syntax the string manipulation expression is accepting.

Any ideas?