To test just a single window:
1- make a UI folder named Test (name doesn't matter, just no spaces)
2- place only the window you want to test in that folder (ensure you include any required .tga files for that window. For example, if you are using custom bars in your group window you would have to include the custom bar .tga file in the "test" folder.)
3- Load up, log in and /loadskin test (this will load only the window you want to try, all other windows will be the default.)
This method works great when trying to piece a UI together from many different authors or when making your own to verify each window works. As you move along in the creation process, just add the new windows and you will see if they conflict with each other as well.
Looking good btw