If you want to use a side bar in your namespace, just create a page named “sidebar” in that namespace in the usual manner. That page will serve as the sidebar page for that namespace, and the pages below it. A sidebar page in the current name space will override the one of the namespace above. (So do NOT edit the main Systems Engineering side bar, create a new one!)
You can use a sidebar to create a menu with links to Wiki pages of interest, so your viewers will have a better understanding of the structure of your namespace.