WPML email notifications
to translate field labels displayed in email body using tags like
WPML needs more parameters and new filter in file includes/MergeTags/Fields.php
For filter 'ninja_forms_merge_label' more parameters like:
apply_filters( 'ninja_forms_merge_label', $field[ 'label' ], $field, $this->form_id )
New filter (to avoid interrupting other 'ninja_forms_render_options' filters)
$field[ 'options' ] = apply_filters( 'ninja_forms_render_options_merge_tags', $field[ 'options' ], $field, $this->form_id );
That way WPML can determine for sure which form (translation package) and which field is in question. Searching by label value could return wrong result if other fields have same original value but different translation (because of context). Even thought it looks like rare case, please consider adding these parameters/hooks to avoid it.