Ryan,
It took me a moment to find the missing pieces, highlighted below. The first is to specify a property on the Tab Container specifying the default tab content. Next, is to declare the default tab as a facet of the Tab Container.
<xp:button value="New Tab" id="button1">
<xp:eventHandler event="onclick" submit="false">
<xp:this.script><![CDATA[dijit.byId('#{id:djTabContainer1}').createTab()]]></xp:this.script>
</xp:eventHandler>
</xp:button>
<xe:djTabContainer id="djTabContainer1" style="width:500px; height:250px;"
defaultTabContent="doc1">
<xp:this.facets>
<xe:djTabPane id="djTabPane1" title="New Document"
xp:key="doc1" closable="true" partialEvents="true">
</xe:djTabPane>
</xp:this.facets>
<xe:djTabPane id="djTabPane2" title="Home Tab">
<xp:label value="This is the home tab"></xp:label>
</xe:djTabPane>
</xe:djTabContainer>
<xp:button value="New Tab" id="button1">
<xp:eventHandler event="onclick" submit="false">
<xp:this.script><![CDATA[dijit.byId('#{id:djTabContainer1}').createTab()]]></xp:this.script>
</xp:eventHandler>
</xp:button>
<xe:djTabContainer id="djTabContainer1" style="width:500px; height:250px;"
defaultTabContent="doc1">
<xp:this.facets>
<xe:djTabPane id="djTabPane1" title="New Document"
xp:key="doc1" closable="true" partialEvents="true">
</xe:djTabPane>
</xp:this.facets>
<xe:djTabPane id="djTabPane2" title="Home Tab">
<xp:label value="This is the home tab"></xp:label>
</xe:djTabPane>
</xe:djTabContainer>
<xp:button value="New Tab" id="button1">
<xp:eventHandler event="onclick" submit="false">
<xp:this.script><![CDATA[dijit.byId('#{id:djTabContainer1}').createTab()]]></xp:this.script>
</xp:eventHandler>
</xp:button>
<xe:djTabContainer id="djTabContainer1" style="width:500px; height:250px;"
defaultTabContent="doc1">
<xp:this.facets>
<xe:djTabPane id="djTabPane1" title="New Document"
xp:key="doc1" closable="true" partialEvents="true">
</xe:djTabPane>
</xp:this.facets>
<xe:djTabPane id="djTabPane2" title="Home Tab">
<xp:label value="This is the home tab"></xp:label>
</xe:djTabPane>
</xe:djTabContainer>
<span style="font-family:courier new,courier,monospace;"> <xp:button value="New Tab" id="button1"><br/>
<xp:eventHandler event="onclick" submit="false"><br/>
<xp:this.script><![CDATA[dijit.byId('#{id:djTabContainer1}').createTab()]]></xp:this.script><br/>
</xp:eventHandler><br/>
</xp:button><br/>
<xe:djTabContainer id="djTabContainer1" style="width:500px; height:250px;"<br/>
defaultTabContent="doc1"><br/>
<xp:this.facets><br/>
<xe:djTabPane id="djTabPane1" title="New Document"<br/>
xp:key="doc1" closable="true" partialEvents="true"><br/>
</xe:djTabPane><br/>
</xp:this.facets><br/>
<xe:djTabPane id="djTabPane2" title="Home Tab"><br/>
<xp:label value="This is the home tab"></xp:label><br/>
</xe:djTabPane><br/>
</xe:djTabContainer></span><br/>
</div>
<p>
In order to get dynamic creation of inner tabs working, I mocked up an example below. However, the function createTab is declared on the Tab Container and can only add children tabs. Since the parent Tab Container has two children Tab Containers, the dynamically created tabs are added to the children Tab Containers respectively. I'm not certain if it is possible to have a parent container with a child tab pane and a child tab container. For more details on the createTab function, have a look at the file Tabs.js.</p>
<p>
<span style="font-family:courier new,courier,monospace;"> <xp:button value="New Inner Tab 1 Pane" id="button2"><br/>
<xp:eventHandler event="onclick" submit="false"><br/>
<xp:this.script><![CDATA[dijit.byId('#{id:djTabContainer3}').createTab()]]></xp:this.script><br/>
</xp:eventHandler><br/>
</xp:button><br/>
<xp:button value="New Inner Tab 2 Pane" id="button3"><br/>
<xp:eventHandler event="onclick" submit="false"><br/>
<xp:this.script><![CDATA[dijit.byId('#{id:djTabContainer4}').createTab()]]></xp:this.script><br/>
</xp:eventHandler><br/>
</xp:button><br/>
<xe:djTabContainer id="djTabContainer2" style="width:500px; height:250px;"><br/>
<xe:djTabContainer id="djTabContainer3" title="Tab 1"<br/>
defaultTabContent="doc2"><br/>
<xp:this.facets><br/>
<xe:djTabPane id="djTabPane5" title="New Document"<br/>
xp:key="doc2" closable="true" partialEvents="true"><br/>
</xe:djTabPane><br/>
</xp:this.facets><br/>
<xe:this.dojoAttributes><br/>
<xp:dojoAttribute name="nested" value="true"/><br/>
</xe:this.dojoAttributes><br/>
<xe:djTabPane id="djTabPane3" title="Inner Tab 1 Pane"><br/>
<xp:label value="Inner Tab 1 Pane" id="label3"></xp:label><br/>
</xe:djTabPane><br/>
</xe:djTabContainer><br/>
<xe:djTabContainer id="djTabContainer4" title="Tab 2"<br/>
defaultTabContent="doc3"><br/>
<xp:this.facets><br/>
<xe:djTabPane id="djTabPane6" title="New Document"<br/>
xp:key="doc3" closable="true" partialEvents="true"><br/>
</xe:djTabPane><br/>
</xp:this.facets><br/>
<xe:this.dojoAttributes><br/>
<xp:dojoAttribute name="nested" value="true"/><br/>
</xe:this.dojoAttributes><br/>
<xe:djTabPane id="djTabPane4" title="Inner Tab 2 Pane"><br/>
<xp:label value="Inner Tab 2 Pane" id="label4"></xp:label><br/>
</xe:djTabPane><br/>
</xe:djTabContainer><br/>
</xe:djTabContainer></span><br/>
</p>
<p>
I hope this helps. Darin.</p>
</div>