Select All in a NavigationListView on macOS?

There are a couple of questions in here.

I want to do a basic master-detail split view, as so many SwiftUI apps do. But I want to let the user select an arbitrary subset of items in the list, select them all, and delete them (or do other operations).

1. Select All, by default, is excruciatingly slow. I have a List view with a selection binding to a Set<PersistentIdentifier>. A ForEach inside renders the items from a SwiftData @Query. I have a couple hundred items, each with a String and Date property. The list item renders the String and nothing else.

I click on an item, hit Command-A, and the app locks up for several seconds while it messes with the selection. It never highlights all the items, but sometimes highlights one (usually different from the one I clicked on).I have an .onChange(of: self.selection) in there to debug the selection. It is called many, many times (2-3 times per second, very slowly), and print the selection count, which starts at 135, and goes down by one, to about 103. If I scroll the list, the selection onChange gets called a bunch more times. Sometimes you see the selection highlights change.

My SwiftUI view hierarchy looks like this:

NavigationSplitView
  OrdersList
 
struct
OrdersList : View
{
	var
	body: some View
	{
		List(selection: self.$selection)
		{
			ForEach(self.orders)
			{ order in
				NavigationLink
				{
					Text("Order ID: \(order.vendorOrderID ?? "<none>")")
				}
				label:
				{
					Text("Order ID: \(order.vendorOrderID ?? "<none>")")
				}
			}
			.onDelete(perform: self.deleteOrders)
			.onChange(of: self.selection)
			{
				print("Selection changed: \(self.selection.count)")
			}
		}
	}
	
	func
	deleteOrders(offsets: IndexSet)
	{
		withAnimation
		{
			for index in offsets
			{
				self.modelContext.delete(self.orders[index])
			}
		}
	}
 
	@State							var	selection							=	Set<PersistentIdentifier>()
	@Query							var	orders				:	[Order]
	@Environment(\.modelContext)	var	modelContext
}

1. If I use the mouse to select a single item, it behaves as expected. The item is selected, the onChange gets called, and if I choose Edit->Delete, the onDelete handler is called.

If I use the mouse to shift-select multiple items, the behavior is similar to Select All above, but the selection Set count starts at the number of items I selected, and then is slowly whittled down to 0 or 1, with some random item being selected.

1. I’d like for the Edit->Delete command to work with a keystroke (delete). How can I set the shortcut on an existing menu item without having to reimplement its behavior?