You cannot generally have tokens within tokens (about the only exception to this is within nested brackets, such as: %Calculate%1+CHARACTERS(%LongDate%)%).
So the text between the ] and % is plain text. Even \n will not work.
As suggested, the technique to use is to replace the return with something that is plain text and unique (so generally not a comma). For example ",KMSEP,".
Search and replace \n with ,KMSEP, and then use [index],KMSEP,% at the end of your token.