Comment 2 for bug 347736

I think it would be hard to get sponsors to change their MARC records in cases like this, especially since we'll only discover problems with their MARC data when we get the book and our loaders do a catalog lookup.

Yes, it is true that <language>engfre</language> doesn't work, as their experiment demonstrated.
And adding a second language code is exactly what they are doing.

It is also true that the biblio tool offers no way to specify additional elements. That is what this request is about.