jQuery Grid Plugin - jqGrid

 colModel: [
...
      { name: 'note', jsonmap: 'note', index: 'notifications.note' },

      { name: 'report_date_created', jsonmap: 'report_date_created', index: 'reports.date_created', align: 'center', width: '100' }, /* full datetime dd.MM.yyyy HH:mm:ss */

      { name: 'reports.date_created', jsonmap: 'report_date_created_group', index: 'reports.date_created', hidden: true } /* short date only for grupping yyyy-MM-dd */

   ],

 groupingView: { groupColumnShow: [true], groupDataSorted: true },

....

when groupping by third column its become visible.

it is better to change logic to show only column with hidden: false or add to colModel property ShowWhenGrouping