It is not possible. Translations module picks up only the fields of each widget that are saved in the database for the widget and in the case with forms widget it only links to a form with all of its controls without coping the form in the widget and thus it doesn`t have the form fields saved as properties to the form widget.
A custom widget needs to be implemented to provide this and save the form fields values into a single widget. To add the properties of a custom widget to be translated refer to this
documentation. To query Sitefinity forms refer to this
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