Hierarchical RadGrid Insert Child Table

Hi,

I'm trying to insert a child table into a hierarchical RadGrid.  If there is already a child table under the master table, the Add New Record button appears.  When there are no child tables already existing, however, the grid just displays "No child records to display".  My desired functionality is to get a new child record to be created even if there are none existing via an Add New Record button.  Is this possible (through a property, button, or otherwise)?

I have provided a picture for reference.  The first two master records are unable to create new records underneath them, even though the third and fourth master records are.

Thanks!