Hey, thanks for the feedback. In the Agent layout, the Cursor icon was removed in version 2.3.
Try switching to the Editor layout, the Cursor icon is still there. Quick way: press CMD+E to switch to Editor mode. In this mode, the icon will be there and you can close the panel with one click.
Alternative: use the CMD+ALT+B shortcut to toggle the panel in any mode.
If you have more UI feedback, you can leave it in the layout and UI megathread. The team is actively reading it.