Can't change media kind of multiple items

iTunes 12.7.0.166 will not allow me to change the media kind of multiple items. I can change each one individually from "music" to "audiobook," but it won't allow me to change twenty, ten, five, or even two at the same time! It's something I did all the time—download ten CDs of an audio book, then change all ten from "music" to "audiobook."

Please help me figure out how to do it in the new iTunes!

—Bardfilm