Line break

We can read this in the http://unity3d.com/support/documentation/Components/class-GuiText.html

When entering text into the Text property, you can create a line break by holding Alt and pressing Return.

alt+Enter dose a sound, but nothing show up that look like a break line.

You can use this to signify a line break:

\n

For example:

someText=“This is line 1.\nThis is line 2.”;

No.

If you mean entering text into Unity’s text field, the ‘alt-return’ shortcut seems to be broken on windows. You can get around this by copying and pasting a return character from some other text program such as notepad.