To set up multiple desktops:
- Click Menu
- Click Preferences
Click Openbox Configuration Manager
If you do not see the Openbox Configuration Manager, install it by running:
sudo apt-get install -y obconf
Click on the Desktops tab, and select the desired Number of desktops.
You now have multiple desktops, use the keyboard shortcuts Ctrl + Alt + ⇨ or Ctrl + Alt + ⇦ to switch between the next and previous desktop.
If the shortcuts keys do not work, refer to the following post for Raspbian keyboard shortcuts to change your key-binding in Openbox.