Currently, when introduced into a Page, the TabControl comes with two TabItems, each containing a Grid Element.
These can be duplicated to create further tabs in the layout.

However, when introducing a new TabItem manually via the Add Element Panel, then adding a Grid Element to it manually from the Add Element Panel, the Grid initially doesn't render on-Stage, and displays an off-Stage adorner. (See attached image)

This issue persists until a different TabItem is selected, then the manually-added TabItem, is reselected.

Marking this one as 'Major' because to new users, it makes it appear as if they cannot manually add TabItems successfully.

Repro Steps:

1) Create a Noesis Studio Project featuring a MainPage.xaml
2) Introduce a TabControl to the Page
3) From the 'Add Element' Panel, search for the TabItem Element, and introduce it to the TabControl.
4) From the 'Add Element Panel', search for the Grid Element, and introduce it to the TabItem added in Step 3).

Observe how the Grid does not appear within the TabItem's Content area, and has an adorner flung in the top-right of the Stage.

5) Select any other TabItem, then reselect the Grid Element added in Step 4).

Observe how the Grid is now rendering in the expected position on-Stage.

Expected Results: Compatible Elements added to a manually-introduced TabItem correctly render in its associated content area.