macOS and iPadOS are full of those undiscoverable "if you do this combination of buttons/swipes while at full moon, something happens". As a Mac user not by choice (work issued) I hate how impossible to discover these are.
As a Mac/iOS/iPadOS user it seems that itβs almost mandatory to watch each Keynote / product announcement video if you want to keep up with new features. Lots of cool features that I only knew about by watching those videos that are completely undiscoverable otherwise.
These kinds of shortcuts are part of Apple software as a whole, and apparently have been a thing since at least OSX. These behaviors were supposed to be covered in the documentation, but I don't know how true this is nowadays.
Special mention to all text input fields in macOS having Emacs-style shortcuts.
It goes back further than that. I remember being able to buy key-combo cheat cards for System 7, and I have no reason to think the shortcuts they covered wouldn't also have been present in System 6.
