This issue is specific to users using the QuillBot extension on a Brave browser. The “X” icon is not showing up or visible in the sidebar, making it impossible to close. This is because the QuillBot extension is natively built for Chrome but is being used on a Brave browser.
On the top right-hand side of the QuillBot extension panel, you will find a "Hide Sidebar" button. This button serves as a workaround to close the extension panel when the "X" icon is not visible.