How to start App Expose without using Force Touch or the keyboard?

Solution 1:

The following command will enable mouse scroll to open App Expose

defaults write com.apple.dock scroll-to-open -bool TRUE; killall Dock

To disable the gesture, use

defaults write com.apple.dock scroll-to-open -bool FALSE; killall Dock

Solution 2:

It's possible to trigger this as a Hot Corner or with a mouse click in High Sierra (available from the Mission Control area of System Preferences), though these only work for the active application. I assume you're asking about the click-and-hold behavior that was available in Snow Leopard.

The closest I can see now is to right-click on an application in the Dock and select "Show All Windows". While it takes two clicks, it does serve to pull up the App Exposé interface for the desired application.