The text to display in the default button.
The prompt appears on all NSSavePanel objects (or all NSOpenPanel objects if this property is on an NSOpenPanel instance) in your application. By default, the text in the default button is “Open” for an Open panel and “Save” for a Save panel.
Use short words or phrases, such as “Open,” “Save,” “Set,” or “Choose,” on the button. The button is not resized to accommodate long prompts.