大文字・小文字変換

[umemura]

String.to-upper-clone メソッドを利用すればできます。
MenuButton のサンプルを追記しておきます。

Code:

{value
    let tf:TextField = {TextField}
    {MenuButton
        takes-focus? = false,
        tf,
        {MenuAction
            label = "To Upper",
            key-accel-string = "Ctrl+U",
            {on Action do
                {if-non-null str = tf.value then
                    set tf.value = {str.to-upper-clone}
                }
            }
        },
        {MenuAction
            label = "To Lower",
            key-accel-string = "Ctrl+L",
            {on Action do
                {if-non-null str = tf.value then
                    set tf.value = {str.to-lower-clone}
                }
            }
        }
    }
}