Currently, when creating a TabItem Content Template from a Page; multiple unexpected events occur:

1) An orange 'ContentPresenter Missing' error appears.
2) The created TabItem Content Template gets correctly assigned to the TabItem, but does open in the Template Dummy Editor as expected.

Furthermore, when Editing the created and assigned TabItem Content Template in-place from the Page, it successfully opens, but displays a void Navigator Panel.
However, when the same TabItem Content Template is opened for Edit from the Resources Panel, there, it contains a Grid and a TextBlock.
Therefore, it appears as though the structural content of the TabItem Content Template differ depending on where it is opened from.

Repro Steps:

1) Create a Studio Project featuring a MainPage.xaml

2) Introduce a TabControl to the Root Grid of the Page.

3) Right-Click on any of the TabItems included in the TabControl, and from the context menu's 'Templates' section, navigate to 'Content', then select 'Create'.
Observe how an orange error message is produced.
Observe how the Template is not opened in the Template Dummy Editor as is usually the case upon Template Creation from the Page.

4) Right-Click on the TabItem that the Template from Step 3) was created on, and from the context menu's 'Templates' section, navigate to 'Content'.
Observe how the Template that was created in Step 3) was assigned to this TabItem.

5) Still in the 'Templates' Section 'Content' Template menu, this time, select 'Edit' to open the Template for Edit.
Observe how the Template now opens in the Template Dummy Editor, but contains an empty Navigator hierarchy.

6) Exit the Template's Dummy Editor, and navigate to the Resources Panel.

7) In the Resources Panel, identify the Template created in Step 3), hover over it, and click on the Pencil icon to open it for edit.
Observe how the Template opens in the Template Dummy Editor, but this time contains Elements in the Navigator Panel.

Expected Results: A Template's Navigator Scope and internal Elements match regardless of where the Template is opened from.
Expected Results: With the default TabControl and TabItem Elements, it is possible to create a Template for the TabItem's 'Content' sub-Template. (similar to how it is possible to successfully create 'Content' Templates for a ContentControl Element)