At a high level:
Define a KMPNavigationEventsManager interface in common code.
Define an expect/actual factory function for above interface.
Implement the KMPNavigationEventsManager interface in iOSMain , here you write the actual iOS code to navigate to specific screen.
Return above implementation in the factory function actual implementation.
Without a global factory function.
You can pass the implementation directly in your ComposeApp root Composable. This is the best way in my opinion since you have the scope of the UiNavController/SwiftUiNavigator in the iOS side.