Can't I just modify list mapping and specific variables in the map when mapping document lists? If you map lists, you can't change the value of any variables in them.

For the image, val6 is added to the output list, I want to turn over all the input list, and I want to put hard coded value in val6

I didn't understand you question quite right.

If you want to modify the document in a list, you can do it like what you do for any element in the pipeline. You can drop, add a string/document variable to it etc.

If what you are asking is to map variables conditionally,  you can use the copy condition property. It will copy the variable only if the condition in that property is satisfied. 

If neither of these is what you are looking for, please provide more detail, explain it with an actual pipeline variable with values in it.