Macro command Variable Modify String has options that would allow you to take form data, concatenate multiple data items, and write the concatenated string to a file. For example, with values a, b, and c from the form:
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Variable Set String %line% to "" // set line null
Variable Modify String %line%: Append Text (") // line contains double-quote
Variable Modify String %line%: Append Text String Variable (%form_data_1%) // line contains "a
Variable Modify String %line%: Append Text (",") // line contains "a","
Variable Modify String %line%: Append Text String Variable (%form_data_2%) // line contains "a","b
Variable Modify String %line%: Append Text (",") // line contains "a","b","
Variable Modify String %line%: Append Text String Variable (%form_data_3%) // line contains "a","b","c
Variable Modify String %line%: Append Text (") // line contains "a","b","c"
Variable Modify String: Append %line% to text file, "c:\test|filaname.csv" // write line to file
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Even though the last command writes to a "text" file, the fact that you use the .csv extension on the file name will make Windows, Excel, etc. consider it to be the csv file type.