While you cannot explicitly tell QIE to use both simultaneously, when using an RSA key for authentication QIE will use the password as the fallback option in case key authentication fails.
In the upcoming 5.23.1 release, we've made it easier to use keys with SFTP connections by allowing you to select a key that has been loaded into QIE, rather than relying on reading it from a file as a custom Apache Camel parameter.