Got it. I would construct this one line at a time. If you're comfortable scripting, you can write a single action to make an array of arrays, and then convert the array to CSV.
Here's a quick Ruby snippet that should do the trick. You just need to flesh out the variables before pushing them into the array. Make sure each array variable has the same amount of items (even if blank) so the CSV columns remain aligned.
array = []
req_header = ["Requisition","Submit For Approval?","Justification","..."]
req_line_header = ["Line Number","Catalog Item Number","Non Catalog Item Description","..."]
req_line = ["Requisition","..."]
req_line_line = ["Requisition Line","..."]
array.push(req_header, req_line_header, req_line, req_line_line)
csv = array.to_csv
## output
{csv: csv}
Let me know if you need more help with this.
