Piwik\Plugins\ExampleSettingsPlugin\SystemSettings::createDescriptionSetting PHP Method

    private function createDescriptionSetting()
    {
        $default = "This is the value: \nAnother line";
        return $this->makeSetting('description', $default, FieldConfig::TYPE_STRING, function (FieldConfig $field) {
            $field->title = 'Description for value';
            $field->uiControl = FieldConfig::UI_CONTROL_TEXTAREA;
            $field->description = 'This description will be displayed next to the value';
        });
    }