commandChar

Syntax

[the] commandChar of <button>

set the commandChar of button "OK" to return
set the commandChar of button "Do Unimportant Thing" to empty

Explanation

The commandChar property allows you to specify a keyboard shortcut to trigger a button. If you specify the return or newline character, the button will become the blue default button. If you specify the escape character, it becomes the “cancel” button for the window. Otherwise, pressing the Command Key and the given character will trigger the button.