Extend macOS toolbar downward in SwiftUI

ToolbarAccessory.swift

import SwiftUI

extension View {
    func toolbarAccessory(@ViewBuilder content: () -> some View) -> some View {
        safeAreaInset(edge: .top) {
            VStack(spacing: 0) {
                content()
                Divider()
            }
            .background(Material.bar, ignoresSafeAreaEdges: [.top])
        }
        .toolbarBackground(.clear, for: .windowToolbar)
    }
}