Users can do a regular expression ‘Search and Replace’ on their 12.6 export file to convert it:
Search for... (.*)\r\n
Replace with... "$1",
After ‘Search & Replace’, manually delete the trailing comma that the Replace inserts. If the user doesn't have too many entries, they can manually run through and make the old file look like the new format. Double-quotes around every line in the old even if it does not have a space is OK.