Duplicate `Content-Type` headers in Postman

If you ever duplicate a header Postman overrides the preceding header and tells you This is a duplicate header and will be overridden by the <header-name> header added by you. A few days ago I imported a collection with an MTOM SOAP request that duplicates the Content-Type header as depicted below and I'm not sure how this was achieved because I can't find documentation on the subject. I'd like to achieve the same ability.

Postman changes the automatically add headers if you add an explicit one, if you want to have two content type then manually add two headers. Both headers will be send