I may have not got the issue correctly, but what I am making out of this problem is you are trying to dismiss ViewBInsideNavigationView using Navigation Views. But thats not how this code should be used.
Navigation Views work like a tree, you create child views from root view, and when you go back, or dismiss the child view, you land BACK on the root view.
As per Apple documentation - https://developer.apple.com/documentation/swiftui/environmentvalues/dismiss, you use dismiss( or PresentationMode) to Pop the current view from a Navigation stack.
You are trying to dismiss root view here, because you have accessed presentationMode, on view where Navigation view starts, and trying to dismiss it. I don't think dismiss in Navigation views are supposed to work like that.
Please go through the above documentation for proper use.
PS: presentationMode is deprecated to dismiss in 17.0
sidg16
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