gp-nested-forms-force-parent-merge-tag-on-submission.php

<?php
/**
 * Gravity Perks // Nested Forms // Force {Parent} Merge Tag Replacement on Submission
 * http://gravitywiz.com/documentation/gravity-forms-nested-forms/
 */
add_filter( 'gform_entry_post_save', function( $entry, $form ) {

	foreach( $form['fields'] as &$field ) {
		if( $field->get_input_type() == 'form' ) {
			$child_form_id = $field->gpnfForm;
			$child_form = GFAPI::get_form( $child_form_id );
			foreach( $child_form['fields'] as $child_field ) {
				preg_match( '/{Parent\:(.+)}/i', $child_field->defaultValue, $match );
				if( $match ) {
					$value = rgar( $entry, $match[1] );
					$child_entry_ids = explode( ',', rgar( $entry, $field->id ) );
					foreach( $child_entry_ids as $child_entry_id ) {
						GFAPI::update_entry_field( $child_entry_id, $child_field->id, $value );
					}
				}
			}
		}
	}

	return $entry;
}, 11, 2 );

👉 This Gist has been migrated to the Gravity Wiz Snippet Library:

https://github.com/gravitywiz/snippet-library/blob/master/gp-nested-forms/gpnf-override-parent-merge-tag-on-submission.php