Unable to add navigation bar to scene: Root controller issue?

I am still struggling with nav bars and just cannot figure out how to edit or verify that I have a nav bar in my view and would appreciate any help.

I have a project with a different set of scenes, similarly consisting of a navigation controller and three linked view controllers (linked via segues and a main table view embedded in the navigation controller), and I was able to add the navigation bar manually in the interface builder to the appearance controllers that were assigned to the table view controller. But in this set of scenes, the navigation controller is configured as the root view controller for the table view.

I have another set of scenes. A navigation controller and two related view controllers are both table view controllers. I have included the first table view controller in the navigation controller, and then added a second table view controller to it (for a new screen that I want to add to my app), and I connected this second table view controller to my first table view controller, the way to show- shogu (like yesterday, with a different set of scenes). Can I set this other navigation controller as the root controller? For example, can I have two root view controllers in a project?

It looks to me like there is a visible navigation bar on my new table view controller (see screenshot below), but I can't click to modify it to add a title to it. But does the navigation bar exist and does exist, and if so why can't I click inside it and use it?

My previous question was answered that you need to add the navigation bar manually to the storyboard scene on any additional view controllers. I did it on time and it worked. But today, when I tried to add a navigation bar by dragging and dropping it onto the stage, it prevented me from doing it.

Here's a screenshot: