Install unity-scope-virtualbox by entering the following commands in the terminal:
sudo apt update sudo apt install unity-scope-virtualbox
Description:
VirtualBox scope for Unity
This package contains the "virtualbox" scope which allows Unity to search for VirtualBox content.
Homepage: https://launchpad.net/unity-scope-virtualbox
Version: 0.1+13.10.20130723-0ubuntu1
Section: universe/gnome