file1.php

add_filter( 'gform_merge_tag_filter', function ( $value, $merge_tag, $modifier, $field, $raw_value ) {
if ( $field->type == 'list' && $merge_tag != 'all_fields' && is_numeric( $modifier ) ) {
    // count the actual number of columns
    $choices      = $field->choices;
    $column_count = count( $choices );

    if ( $column_count > 1 ) {
        // subtract 1 from column number as the choices array is zero based
        $column_num = $modifier - 1;

        // get the column label so we can use that as the key to the multi-column values
        $column = rgars( $choices, "{$column_num}/text" );

        // get the list fields values from the $entry
        $values        = unserialize( $raw_value );
        $column_values = array();

        foreach ( $values as $value ) {
            $column_values[] = rgar( $value, $column );
        }

        $value = GFCommon::implode_non_blank( ', ', $column_values );
    }
}

return $value;
}, 10, 5 );