"A recovery key has been set" but remains invisible with macOS FileVault I have just turned on FileFault on macOS High Sierra with option "Allow my iCloud account to unlock my disk." While encryption is running, macOS informs me that "A recovery key has been set".

Is it correct to assume that with this option set macOS handles the recovery key internally (and securely) and that there in no need (even no way) for me to recover it for writing it down?
Yes, it is correct to assume that macOS handles the recovery key internally and securely. There's no need for you to write something down.

In case you need to do recovery because you have forgotten your login password, you can use your iCloud account to unlock FileVault. Just make sure you can remember your iCloud login details!

When you choose to use iCloud as your recovery mechanism, the settings will still show that a recovery key has been setup - so that's perfectly normal! There's no option in the settings to display the recovery key to you.