how can i update managedobjectcontext later?

You can make view rebuild depending on your UserSettings mentioned toggle property, like

HomeTabView()
    .environment(\.managedObjectContext, persistenceController.container.viewContext)
    .environmentObject(service1)
    .environmentObject(service2)
    .id(userSettings.your_toggle_Sync_Property)    // << here !!

so, once property changed the view will be rebuilt, as property is observed, and new context will be injected.