Do I understand it right? You want to output somehow that alt+enter in a CSV file? Somehow having a line break in an Excel cell, don't you?
If my assumption is correct the answer is simple: It's not possible. CSV doesn't allow any formatting. An "enter" will destroy the structure of a CSV file because Enter is the symbol for line end. If you want to have the cell format you should output some sort of Excel format, preferrably XLSX.