Vaadin Declarative Design... for developers
This tool is for developers, who want to write (declarative) UIs or themes with instant visual feedback. A defined directory (e.g. your resources directory) will be watched for file changes and on write all connected browsers will refresh -- no reload, no compile, zero roundtrip.
Why?
While the Designer for sure is nice, once you know all the components from Vaadin by heart, clicking stuff together in a WYSIWYG editor is not every developer's dream. Taking from awesome tools like ClojureScripts Figwheel, that give the developer instantaneous feedback, providing a tool, that
allows for quickly testing UIs or ideas
filling them with different mocked data (and keep them around for later)
or just eliminate tiresome reload round trips to tackle some "why is the Panel in that TabSheet not scrolling" problems
increases developer productivity.