By package manger do you mean Synaptic?
Debian-based systems also typically include command-line package managers
; they all access the same repos.
Typically, desktop environments provide methods for configuring how many workspaces or virtual desktops are available. Where to do that depends on the individual environment. In KDE, you do that in the KDE system-settings dialog.
I understand that Zorin uses Gnome. You may have to install the gnome-tweak-tool to have this capability.