I am trying to use three finger scrolling on the desktop, but it is not responding. It only works when i am holding the cursor on a app or the plank. Can i edit something in the config file to change this?
Assuming you are using the gnome-shell you can configure it to Have file manager handle the desktop. This way the desktop is managed by nautilus and your gestures should be recognized.
The easiest way to configure this is to use Gnome Tweak Tool.
sudo apt-get install gnome-tweak-tool
Launch Gnome Tweak Tool from the Gnome Shell menu. It will be called Advanced Settings. Then, click on the Desktop button. Enable the option that says "Have file manager handle the desktop. Now, any files placed in the Desktop folder inside your home folder should appear on ther desktop.
As I'm lazy the former paragraph was taken from:
Just changed the formatting and stripped the image.
If you want to use (three finger) scrolling to switch desktops, I remember there was a setting someday, I recommend using the touchegg action called CHANGE_DESKTOP. If you use SCROLL it will scroll on any windows.
if you are using a touchscreen, might be an upstream based bug: http://libcoding.wordpress.com/2013/11/02/issue-with-touchpad-in-ubuntu-13-10-in-xps-12/comment-page-1/#comment-22