The documentation at https://www.raspberrypi.com/documentation/computers/configuration.html#set-resolution-and-rotation still refers to the previous Screen Configuration (raindrop) program that was used in Raspberry Pi OS Bookworm. However in Raspberry Pi OS Trixie this has been replaced with the new Control Centre application.
This outdated documentation is causing users to get confused: raspberrypi/trixie-feedback#43