Missing action item

In the last few Windows updates I've noticed that "Copilot in Windows (preview)" shows up at the rightmost edge of the taskbar. That's fine, since I am experimenting with Copilot. However, before the last few updates, I was able to click on an icon (a vertical bar) to display the desktop, this item has gone missing.

Is there a way to restore this icon, or is it not available anymore??l