Any development environment for widgets?

I’ve just started playing with habpanel after installing a tablet on the wall in the kitchen. I can do most of what I need with dummy widgets, selections and switches but there are a couple of widgets that I’ve downloaded from the gallery that I need to tweak a little to fit my needs.

Looking at the JSON in a text editor shows that there’s a great big long line of code at the top of the widget I’m interested in, is there a way to edit this and see the changes reflected immediately, like a WYSIWYG editor?