If you wan to copy tags from one set of files (perhaps MP3) to others (here perhaps ogg vorbis) it might be an idea to use the function "Copy tag" and "Paste tag": If order and number of source and target files match, you can copy the tags 1:1 in one go.
If you stay with the text file option, then you have to make sure that you have one line per file (one record). You would have to replace the line breaks (carriage return, line feed) with some meta-character like "#".
After the import you replace the "#" again with line breaks (carriage return, line feed).
There is no other way.
Here is a link to a similar problem: /t/10185/1