Currently, all my files with 2 genres display "genre1\\genre2" in the Genre column. I used to have it where I had two genre columns that displayed them separately (so that I can sort them separately), but I can't remember how to change the value for the first column and specify the value of the second.
Sorry, I do not know how you did that.
You can try to learn again how to do this.
Read Mp3tag help manual, chapter Columns.
Read Mp3tag help manual, chapter Scripting, Metadata (including multiple tag fields).
Read some posts from the forum ... http://www.google.de/search?q=site:forums.....de+column+meta
Short help ...
Column name: G 1
Column value: $meta(GENRE,0)
Column name: G 2
Column value: $meta(GENRE,1)
Column name: G 3
Column value: $meta(GENRE,2)