"hidden menu" is a correct and usable phrase in written English.
You could use it to describe a menu in a restaurant that has not been advertised or is not easily visible. For example, "The restaurant has a hidden menu of specialty cocktails that only regular customers can access."
The hidden menu on the left, large photos on the mobile wall — it's seemingly all there, just as expected.
The hidden menu lets you change the theme color of the app and its default sounds to chicken or monkey noises.
The company has become known for limited-time only drinks, like last year's Unicorn, and its hidden menu of drinks that aren't posted on its menu board or mobile app.
Facebook had seen the need for a first-class mobile chat experience way back in 2011 with the launch of Messenger, but many other popular features were left to languish in the hidden menu of the main app.
Players can listen to the game's songs by accessing a hidden menu in the "Gil: Caught Between Love and Adventure" scenario.
Unless you go the Panera route and send out a press release touting your secret menu items (complete with calorie counts), most people will be left to their own devices when it comes to figuring out the hidden menu items.
These hidden menus are called contextual menus because they appear in the context of what you are doing.
They'll use hidden menus to adjust the grayscale settings on your set and truly bring out the best in your new TV.
It also is no longer tucked away under hidden menus, but prominently featured at the top of Amazon.com via a big banner ad.
Monolithic apps worked on the web where there was plenty of space, but are forced to bury features in hidden menus because there's no room on mobile.
A third party application would need to launch the hidden system menu.
