add_filter( 'arm_prepare_custom_rule_data', 'your_function', 10, 2);
function your_function($rule_records, $args) {
    //$rule_records Array of access rule items.
    //$args Array of filter arguments for grid listing
    global $arm_access_rules;
    if ($args['slug'] == 'custom_rule') {
        $dbrules = $arm_access_rules->arm_get_custom_access_rules('custom_rule');
        $protection = (!empty($dbrules['custom_item']['protection'])) ? $dbrules['custom_item']['protection'] : '0';
        $plans = (!empty($dbrules['custom_item']['plans'])) ? $dbrules['custom_item']['plans'] : array();
        $rule_records['custom_item'] = array(
           'id' => 'custom_item',
            'title' => 'Custom Item',
            'description' => 'This is Custom Item',
            'protection' => $protection,
            'plans' => $plans,
        );
    }
    return $rule_records;
}