Field help (HRGRB1ROW) 

The Headings table displays all the headings contained in the “grouping of headings” or in the “grouping detail”.

SEEWARNINGIt is not possible to add headings to this table. You can only view them. To assign headings to a grouping or a sub-group, (a "grouping detail"), use theHeadings function (GESRUB) ortheGrouping of headings function(MAJRUB6)(Setup > Payroll Plan > Heading update > Grouping of headings).