Hi Inexcon,
Thank you for the elaborate description and the supporting Image.
Please excuse me for not understanding your query clearly.
Regarding the query, the shape control within which you wish to draw your controls is actually not a container control. Hence, the behavior of the control when you wish to draw a textbox in it, is the expected behavior.
This behavior is to avoid overlapping of controls, which is not a recommended practice. You will observe the same behavior when you will attempt to draw a TextBox on a TextBox or RichTextBox.
Hope that clarifies, please feel free to share your comments and suggestions.
Best Regards,
Tuhina