Sorry for the inconvenience. Known Navigation header breakage, its being "rebuilt" but forward nav should be ok now.
There may be other unforeseen breakage primarily in the handbook portion of the wiki.
The Table Of Contents section of each "PC-BSD® Users Handbook" page may be the best workaround.
Switching between the icons in the selector changes the icons displayed within the control panel window to match those used in that desktop. If "All desktops" is set by the desktop selector, you will see every utility that is available, depending upon which desktops are currently installed. You can change which desktops are installed using AppCafe®.