[Filechooser Settings]
LastFolderUri=file:///home/ffg/zTEMP
LocationMode=filename-entry
ShowHidden=false
ShowSizeColumn=true
GeometryX=444
GeometryY=232
GeometryWidth=792
GeometryHeight=585
SortColumn=name
SortOrder=ascending

I've tuned xfce4 in order to provide some kind of kiosk mode for public access. It's been quite a success so far, but I'd like to go further and prevent users from browsing randomly in the filesystem.
To do so, I need to disable the shortcut entries in the left panel of the "save as" window. For example, the public users can plug in their USB flashdrive and save a pdf file on it, so it would be better if they don't see anything else but the mounted flashdrive folder.

For better comprehension, I have included a screenshot, on this picture I would like to remove the left panel or remove the Desktop, root filesystem and home folder shortcut entries.
SCREENSHOT HERE : http://flomoto.no-ip.org/pub/xfce4-tuning.png

If anyone knows which configuration file I could edit to reach this behavior, that would be nice.

Thanks