I am using CentOS 6.4 with GNOME.
How can I increase/decrease the number of desktop workspaces?
Install gnome-tweak-tool (live.gnome.org/GnomeTweakTool). Go to Shell tab on the left. There is "Dynamic workspaces" and workspace number options. Thats the one I use to make such changes on my desktop.
Have you try this?
If you right-click the workspace switcher and choose preferences, you can adjust rows and columns from there.
http://www.linuxquestions.org/questions/linux-desktop-74/add-more-workspace-in-fedora-13-a-825426/
With GNOME 42, the number of workspaces is changed in Settings > Multitasking.
By default, the setting is Dynamic workspaces. After changing it to Fixed number of workspaces, it's possible to change the number of used workspaces.
I found gnome-help (see below), which eventually led to a workspaces discussion that revealed these user-privilege (not sudo/root) command line instructions for setting rows and columns:
to set number of columns (in my case, 3), change final parameter:
gsettings set org.compiz.core:/org/compiz/profiles/unity/plugins/core/ hsize 3
to set number of rows (also 3, here), change final parameter:
gsettings set org.compiz.core:/org/compiz/profiles/unity/plugins/core/ vsize 3
The difference for rows vs columns is the next-to-last parameter, either hsize (for columns) or vsize (for rows).
Breadcrumbs from gnome-help:
Ubuntu Desktop Guide » Desktop › Applications and windows » Windows and workspaces › Workspaces »
Heading: "What is a workspace, and how will it help me?"
SubHeading: "Change the number of workspaces"
Ubuntu 16.04 / gnome 3
I am using "Workspace Grid" extension for this.
It arranges workspaces in a configurable grid. You can modify the grid as you like.