How to set the Parent Control from WinForms Designer in Visual Studio?

Can you not use the document outline window? link. This will allow you to re-arrange the control hierarchy and child controls.

this can be access via code, but not in the designer

http://msdn.microsoft.com/en-us/library/system.windows.forms.splitcontainer.aspx

Property is inherited from Control

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.parent.aspx