I find this new widgets screen very confusing. I had the idea that one would be able to use all available blocks in the widget areas. For example, I would be able to add a Jetpack feedback form or a custom reusable block to the sidebar or footer. But that doesn't seem to be the case. And if it is, then it's all very unclear how to implement. I see very few widget blocks right now. The Gutenberg team should add a BETA tag to the plugin.