I have installed Swing Designer, SWT Designer and WindowBuilder Core exactly as described in this tutorial.
As I wanted to create new GUI, I could not find the WindowBuilder option in the "Select Wizard" menu (File -> New -> Other...).
[I wanted to post an image of how the Wizard appear to me, but I don't have enough "reputation" or what... I hope I described my problem clearly enough]
I did everything as was done in the video. I have checked twice, that the WB is installed. When I tried to install it again, a warning was displayed that it is already installed. Also, in the folder where the Eclipse files are (C:\Program Files\eclipse\plugins\org.eclipse.wb.core.lib_1.8.0.r44x201412082350\lib
), there is an evidence of the WB - something is there.
I have tried to update those plug-ins. They are the latest version now, the problem remains nevertheless.