How can I put an NSToolbarItem on the leading edge of an NSToolbar in Catalyst?

I'm working to make my iOS app available via Catalyst, and I'm adding a leading-edge sidebar via UISplitViewController and putting a toggle button in the window toolbar to control it. I'd like that sidebar toggle button to go on the leading side of the toolbar, before the window title.

In the Adding a Toolbar Catalyst tutorial, there are screenshots of this behavior:

But when I download the finished project and run it on my machine (macOS 14.4), the toolbar buttons are clustered on the trailing edge:

How do I achieve the behavior shown in the tutorial's screenshot, where the toggle sidebar button (or, ideally any custom toolbar item I choose) shows up on the leading edge? Even more ideally, is there a way I can make the sidebar toggle button show up in the header section for the sidebar, like it does in Xcode - right next to the stoplight buttons?

It turns out that if I hide the window title and then add the .flexibleSpace (NSToolbarFlexibleSpaceItemIdentifier) item, I can get one or more toolbar items to show up on the leading edge. I don't actually need the window title in my app, so that solves my issue.

How can I put an NSToolbarItem on the leading edge of an NSToolbar in Catalyst?
 
 
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