Return First Value Found from Series of Columns

I have a list of email addresses, each stored in different column labeled by the type of contact (e.g. teacher, department head, principle, etc.)

Each row is a unique location.

I have the columns prioritized from most important to least important (left to right if it matters)

Many columns have lots of missing values

I would like to create one column labeled “highest priority contact” that retrieves only one value for each row: the highest priority email address.

This seems like it should be very straightforward. I can do it in Excel with a long series of if-then statements… but I’m trying to learn KNIME and I’d like to use a loop and a flow variable to do it (rather than construct a long series of if-then statements.)