This is NetBeans 7.0.1. I've looked through the help files and the available plugins and haven't found anything that provides this sort of function. It sure would be helpful to be able to create "sub-projects" or whatever you want to call them, so I could quickly open a group of related files all at once.
"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." -- Ted Nelson