I recently discovered another smart feature in IntelliJ 9.0.3 while working with Spring web flow. The yFiles designer pane came up after opening the Spring web flow XML. As long as I had the SWF namespace, IntelliJ was smart enough to know what I needed.
Same trick worked for JBOSS BMP, too.
How would I tell IntelliJ to do the same thing for other custom XML of my own design? Do I needa plugin or something else? Any advice is welcome. Thanks.