How do you extend a modern collection view cell's default content configuration?

Apple's Displaying Cell Info tutorial shows using a default cell content configuration to set two lines of text

    func cellRegistrationHandler(cell: UICollectionViewListCell, indexPath: IndexPath, id: String) {
        let reminder = Reminder.sampleData[indexPath.item]
        var contentConfiguration = cell.defaultContentConfiguration()
        contentConfiguration.text = reminder.title
        contentConfiguration.secondaryText = reminder.dueDate.dayAndTimeText
        contentConfiguration.secondaryTextProperties.font = UIFont.preferredFont(forTextStyle: .caption1)
        cell.contentConfiguration = contentConfiguration
    }

How would I get started extending this to include a third line of text? I would like to keep the built-in text, secondaryText, and accessory control (the tutorial has a done button on each cell), while also adding custom UI elements. I'm assuming this is possible since Apple uses the term "compositional collection views," but I'm not sure how to accomplish this. Is it possible, or would I instead need to register a custom UICollectionViewCell subclass?