FX 8 javadoc for TextField contains "Unlike in previous releases of JavaFX, support for multi-line input is not available as part of the TextField control, however this is the sole-purpose of the TextArea control."

Today you can use the Inspector and take "Switch to multi-line mode" for property text of a TextField, in which case the Text area becomes bigger, you enter your mult-iine text but rendering is done on a single line.

I suspect there is other places where the same switch can be taken but is not relevant (Prompt Text for TextField, Ellipsis String for a Label (?), ...).