How to cause Subdatasheet to display with Form's Datasheet view
<p>In my database is a Form based on a query which has a subdatasheet defined.  When the Form is in DataSheet view, each record shows the plus sign which can be expanded to show related records according the subdatasheet defined on the source query.  In other words, the Datasheet view automatically shows the Subdatasheet--as expected and as desired, so I know it can function like this.</p>

<p>I then created a new Form based on the same query as the existing, working Form.  However, the new Datasheet view will not show the Subdatasheet... no plus sign, nothing.  Next I created a test database with a couple related tables, and I also ensured that the tables have a Subdatasheet defined.  If I open the tables directly I see the plus signs and Subdatasheet as expected.  But once again if I define a form on those tables, it will not show the Subdatasheet when viewed in Datasheet mode.  There is no separate setting for an Access Form to define the Subdatasheet, rather it can only inherit the Subdatasheet setting from its record source object (i.e. table or query).</p>

<p>Is there any way to force a Form (in Datasheet view) to show the Subdatasheet already defined on the record source object?  Why might the new form function differently than the original even when it's based on the same query?</p>

<p>I'm using Access 2013 and database with 2007-2013 file format.</p>