Allow the creation of new components by grouping existing component.
The best example is a filechooser:
a textfield displaying a filepath with a button to the right that allows the user to browse the filesystem to select a file.

I would like to be able to mark the textfield and the button and define/save this group as a new component. I could then reuse this new component in another form or even project.
In case of the filechoose example, it would be even possible to reuse the actionlistener on the "browse"-button as long as it's only used to display an "open"-dialog and update the textfield.