Add a comment field in Xcode storyboards

UIView+comment.swift

    @IBInspectable var comment: String {
        set {}
        get { return "" }
    }

Maybe a little clearer...
Comments will be stored in the storyboard file but don't have any value at run time.

extension UIView {
    @IBInspectable var comment: String {
        set {}
        get { return "" }
    }
}