How to set up Touch Bar to show function keys in a specific VirtualBox virtual machine
http://www.mastropaolo.com/2016/12/16/how-to-have-function-keys-in-virtualbox-guess-with-macos-touchbar/


  
  Open a Finder window to the /Applications folder. Right click on VirtualBox.app and click “Show Package Contents”.
  Find the Resources folder, and drag it into Finder’s favorites sidebar.
  Using the Resources folder you put in favorites, add vmstarter.app and VirtualBoxVM.app to the list of exceptions.
  Now you can remove the Resources shortcut you added to favorites.