How to add Combo Feature in a ContainerShape Graphiti

Question

I want to add a drop down combo box filter inside a container in the Graphiti Editor.

It appears if I override this method:

public IDirectEditingFeature getDirectEditingFeature(IDirectEditingContext context)

...as shown in the figure below:

...but my requirement is not to bring the drop down feature on clicking over the region, but a stable combo control on the Shape/Container as shown below:

Is there any way in Graphiti to add such controls on Shape?