I am trying to create the same experience where a sheet is presented in one of the tab items of a TabView - not covering the tabs. I am using .presentationDetents() and SwiftUI4.0 for that.
See example of Apple's own app doing that The sheet is covering the child view inside TabView.
However, instead in my own code I am getting this - the tabs of the parent view are covered by the modal sheet
The link https://developer.apple.com/forums/thread/711702 suggests that it is not possible to achieve the same behaviour you see in Apple's Maps and Find My apps with the current SwiftUI API.