Submenu and widget menu sidebar link structure

When I create a submeny (in the sidebar) of a parent page. Can I “re-use” different parent pages instead of creating the same child pages over and over again without loosing the menu feature?

See attached PDF with the link structure for better understanding of the problem.
http://www.filedropper.com/websitemenu or
(Same PDF in both cases, added for redundancy)

In this case I want to reuse the page “Item 3” that is generic for all pages. But I still want the sidebar widget meny to show Topic 1 is the user clicked on Topic 1, Topic 2 if the user clicked on Topic 2 etc.

The problem that I am having is that if I use a generic “Item 3” then the menu feature will disappear when the user clicks on it and only show “Item 3” without a menu and I am not able to add a submenu to “Item 3” since “Item 1” and “Item 2” will be specific for every individual topic.

Thanks for your help!