How to Expose hidden App in Dock as it was in High Sierra?
I haven't found any other option than this, although I'll be honest with me on macOS 10.16 it doesn't work. But I am sure that it will work with older versions.
Just enter this into the terminal here.
defaults write com.apple.Dock showhidden -boolean yes &amp;&amp; killall Dock 

You can give it a try and give me your experience.
You can also undo it again no problem.
 defaults write com.apple.Dock showhidden -boolean no &amp;&amp; killall Dock 

Activate Dock Exposé
The option shown in this example is available from Mac OS X 10.6 (Snow Leopard).
After changing the properties of the dock, the dock must be restarted.
If you want to activate the Dock Exposé (standard), you can do this as follows:
defaults write com.apple.dock show-expose-menus -bool yes; killall Dock