This needs to be adressed it is very annoying!!
OS Windows 11 Pro v 23H2 (Build 22631.2506)
What you are seeing is not the 'Minimize to system tray' setting.
TBH that setting is no longer really useful. It was there for much older Windows where you couldn't pin apps to the taskbar, but is not needed nowadays. (As newer CCleaner versions can't run on those old Windows systems anyway then that setting could be removed).
What you are seeing in the tray is an icon that Windows has put there because a CCleaner process is running in the background.
CCleaner cannot control or override that, it's Windows that is doing it.
That background process is usually Smart Cleaning, or 'Keep CCleaner updated automatically', or both.
As long as you have either Smart Cleaning, or 'Keep CCleaner updated automatically', or both enabled then Windows will put an icon in the system tray.
If you disable both of them then there will be no background task running for CCleaner and so Windows will no longer put the icon there.
Thank you.