How do I use Qt's example Borderlayout in Qt Designer?

Question

I'm new to Qt and don't grasp Qt Designer's relation to source code fully yet. I implemented Borderlayout example and would like to design my UI in Qt Designer using it, but don't know how. I'm using Qt 5.3 and C++.

Answer 1

Qt Designer still does not support custom layout plugins:

Designer should be able to use custom layout plugins.