MacOS SwiftUI: Modify sample project to allow toolbar items

I've uploaded a simple Xcode SwiftUI project with a NavigationView.
It has some ToolbarItems which needs to be changed programmatically.

I've added 5 simple tasks inside the source code that needs to be fulfilled to complete the project:
// 1. Add this menu item to the menu in the toolbar
// 2. Remove this menu item from the toolbar
// 3. If the removed item is the current selected one the next available item
// needs to be selected
// 4. Change the name of the menu item
// 5. The title name of the menu needs to have the name of the selected item
// The text 'This needs to be changed programmatically' needs to be changed for this

With this done the Tests:
// Test A remove menu item
// Test B rename menu item
// Test C add menu item
// Test D remove new added menu item

should run successfully.