I am trying to develop a module extension which needs to store some settings, I went through the documentation and found [this][1] to be the way to create settings. 

Now when I put default as NULL the setting is not reflected in the table, if I put any value as default the setting is added to `civicrm_setting` table.

Also, though the settings have option to specify attributes for admin form, I couldn't figure out a way to get them to the admin form. 

Is there anything else which I need to do apart from adding the setting folder and the following code to extension.php

    function multisite_civicrm_alterSettingsFolders(&$metaDataFolders = NULL){
         _multisite_civix_civicrm_alterSettingsFolders($metaDataFolders);
    }


  [1]: https://github.com/eileenmcnaughton/org.civicrm.multisite/blob/master/settings/Multisite.setting.php