My VST3 is in this exact location. Melodyne is showing up in the system component Information window with a tick next to it.
However - no “extension” option at the top of the audio editing window. however, I can select the audio in the project window go to the menu at the top “audio / extensions” and then select it from there.
Is that the right way of doing it? I thought an extension option would appear like in this picture: