WPForms: merge values for 2 fields into a 3rd one

wpforms-merge-field-values.php

<?php

add_filter( 'wpforms_entry_save_data', static function ( $fields, $entry, $form_data ) {

	$value1 = '';
	$value2 = '';

	// These are field IDs to take data from, and to merge into.
	$field1_id = 1;
	$field2_id = 2;
	$merged_id = 3;

	foreach ( $fields as $field ) {
		if ( $field['id'] === $field1_id ) {
			$value1 = $field['value'];
		}
		if ( $field['id'] === $field2_id ) {
			$value2 = $field['value'];
		}
	}

	$fields[ $merged_id ]['value'] = $value1 . ' - ' . $value2;

	return $fields;
}, 10, 3 );

Hi
this is very helpful, since the field ID is not unique in wpforms is there a way to validate the filter with form ID ?

Yes, you can check the $form_data['id'] to be the value you need.