Floating JavaFX ComboBox

Question

How to make floating JavaFX editable ComboBox? ComboBox options list is floating, but not the textfield. How can I make the textfield floating as well.

comboBox.setEditable(true);
comboBox.getEditor(). ...?

Image 1: In this image, TitledPane "Funcionalidad is not expanded"

Image 2: In this image, when TitledPane "Funcionalidad is expanded, the TextField "Código" is displaced down because of the ComboBox Textfield, but not because of the ComboBox options list. ComboBox options list is over the TextField "Código"

How can I make that the ComboBox TextField also be over the TextField "Código"?