Adding display do Grid

Hello. Is there any way to add display to forms? To this time enough to do this was drag & drop that field but now i have some Grid:Grid and cannot insert or add any of new field. There is only fields from that data source which is declared in Grid properties. Thanks for help

Are you unable to add the field to the grid? Does the grid has a Field group assigned to it?
Check the data group property of the grid.