Hi @NeilP ,
Could you share screenshots of Flow's current configuration?
I am not sure where you got the data and inserted them into the Excel table.
If you are inserting the submitted data from MS Forms into the Excel table, it seems that you have a solution in the Thread you provided.
List of response notification Response Id will record the order of submissions.
If you want to automatically add the item number when inserting data into an Excel table that already has records, we could use the variable to get the current max item number, and then add 1 to generate a new item number.
For example, my field name is Item Number, please refer to the following method to get the max item number.
Image reference:

Please take a try.
Best Regards,