How can I disable animation when switching desktops in El Capitan?
There is a program named TotalSpace, that has the feature you need. Once installed, you should open it up, go into "Transitions" and disable "Use transitions", this will remove the animation you get when you switch Workspace (aka Dekstop)

If you're on OS X 10.11.x El Capitan or later, you will also need to disable a feature known as "System Integrity Protection" which prevents you to edit or access system files. To disable it:


Restart the Mac, then boot it in recovery mode, by holding down cmd (or Windows key) and R keys, before hearing the sound of your Mac startup. Hold them down for 5 secs.
Click on "Utilities" on the top of your screen, then select terminal.
On the new opened window, enter csrutil enable --without debug .
Reboot
Enjoy :)


csrutil enable --without debug is the better solution suggested by [http://totalspaces.binaryage.com/elcapitan][totalspace].