We have added a new tool to the scripted RC: the Gui Editor! This has been existing for a while but was never finished, but now it's finally available. Open the scripted RC (F6) and click on this icon:
You will then see the Gui Editor window. There select a GUI type (e.g. "Window") and click on the "+" button for adding the GUI control (click on the image to see the full image):
Once you are finished click on the "Compile" button to upload the script to your server. The Gui Editor supports the new GUI styles, so you can easily make windows which use the users choosen GUI style.