up:: PowerAutomate
Power Automate Functions - Or - YouTube
You can use or function to check if one of the parameters matches given criteria:
or(not(empty(item()?['invoice number'])),item()?['invoice number'],not(empty(item()?['Invoice No'])),item()?['Invoice No'])
This function checks if 'invoice number' column is not empty or 'Invoice No' column is not empty.
Either way it will result with a first encountered true or (if all are) false.