Since version 6.5, Castle Game Engine includes an Editor.
You can use the editor to design a user interface,
which is just a tree of
Such user interface can be saved to a file with extension
and later loaded in your game using a call like
The editor can be used with any Castle Game Engine project containing a CastleEngineManifest.xml file. The editor has the same "concept" of a project as our command-line build tool, in fact the editor can also be used to compile and run the project.
See also the movie explaining th editor: