When a new field is added on top of the screen a section called "Copy from existing field" is displayed. This allows the copying of all field settings from another field definition into the newly added field. This section is only displayed for new fields.
Select from the selection list the Form from which a field definition should be copied. You can also type in the name and the list will be filtered. Once a form is selected, the second drop down list will show all fields within the selected form. The default language label of fields is used in this list. When a field is selected, click on the copy button. The screen will reload and the Copy from existing field section disappears. If the copied field belonged to a section, that section value is also copied.