Bug#780203: general: Cannot have more than 2 desktops
Just for completeness, here is how you would get 8 workspaces (desktops)
Firstly, and the easiest way, is to have at least 7 windows open, one
per workspace. An 8th workspace will be automatically available, and
will be empty.
If you wish to have a static number of workspaces, change the setting in
the Tweak Tool . On the left hand side of the window, select the
Workspaces button. Then change workspace creation to static. Input the
number of workspaces in to the box below.
1: If you cannot find it, you may need to install it, the package name
is gnome-tweak-tool (sudo apt-get install gnome-tweak-tool)