How do I get the column header for the first cell per row that is not empty

[Majao]

Dear all, 

I am trying to get the header name of the first non-empty cell in my data set, and adding that to a new column. From the screenshot below, I would have that the first row here would have "202011" as the value in the new column. The second row would be "202109". 

Can you help me with this? I also added a simple table as a simplified example of the format of the data and what I want to get.  

Screenshot (my data)

Simple example table

	2020	2021	2022	My new column
Customer 1		10		2021
Customer 2	10			2020
Customer 3			10	2022
Customer 4		10		2021

[binuacs]

@Majao 

[Qiu · Accepted solution]

@Majao 
I can see there are some columns is having multiple values. so I made somethig as below based on @binuacs  work.

[Majao]

Works like a charm - thank you!