Under Compiz :: General Options :: Desktop Size I already have 2x2 layout of 4 virtual desktops setup, as in screenshot.

However if you notice as in the switcher app parked in the top left corner, only one desktop shows, and indeed only one is available to send windows to or hover over to.
Right-clicking that docked switcher to "Add a workspace" doesn't behave right anymore. It's like the desktops are too independent and trying to send windows to Right/Down isn't an option anymore from the Alt Space menu. Nor do hotkeys CTRL-ALT-Arrow work to slide over anymore. Double-Clicking does switch desktops though, but it's like they're in otherwise unrelated Xwindows sessions(cannot be, of course).
For a while I've been stuck with a stubborn 1x1 or 1xN layout, unable to figure out why it won't go to 2 columns, until I discovered the Compiz :: General Options :: Desktop Size :: "Number of Desktops" had mysteriously gone to 0. Horizontal and Vertical were both still 2 there. (Weird things happened when I next made that 0 into 4--Switcher at first drew 16 virtual desktop boxes, after which I decided to collapse everybody into 1 desktop and start again from there.) My ~/.dmrc contains only:
[Desktop]
Session=cairo-dock
I noticed each has a title now: Work / Game / Video / Chat, maybe they were present before I had to reboot from a total Xwindows unresponsive freeze(though switching back and forth from text consoles Ctrl Alt F1-F6 still worked) twice, but I don't recall titles before.
After some updates to cairo-dock and many other packages since Feb, notice 16 workspace boxes manifested themselves again, though only 4 seem switchable via ctrl-arrow keys:
