concat multi-row and promote to header

[#1]

concat selected columns and n-th rows with "_" delimiters and promote to headers.

and fill-right for any empty field.

Example:

Input:

Field1	Field2	Field3	Field4	Field5	Field6	Field7	Field8	Field9
Country	UK				US
Shop	Shop1		Shop2		Shop3		Shop4
Sales	James	Quuin	Jack	Don	Kim	Bob	Kinston	Hua
Sales Amount	1000	1010	1200	2043	2000	3000	4000	5000

output:

Country_Shop_Sales	UK_Shop1_James	UK_Shop1_Quuin	UK_Shop2_Jack	UK_Shop2_Don	US_Shop3_Kim	US_Shop3_Bob	US_Shop4_Kinston	US_Shop4_Hua
Sales Amount	1000	1010	1200	2043	2000	3000	4000	5000

config: 

bugs: it will apply to any new fields until you open the config again. (where it auto add new field as uncheck)
for example, if you have new field call "Field10" for above. it will consider as check until you open the config again.
i have raised idea for this to fix this bugs: *unknown field for interactive list tools. - Alteryx Community