The "Persistence 2.0" experiment represents the new and improved version of Workspaces in DevTools. If you are working on a site, for example at
http://localhost:3000, you can drag and drop your source code from the filesystem directly into DevTools. DevTools automatically figures out the network-filesystem mappings and allows you to start editing your code. You can edit Sass code (assuming you have Source Maps enabled) and DevTools will write your changes to disk.
This is an experimental feature in Canary
Update: Style Rule Toolbar is in Chrome Stable!
Please share the Dev Tips project with others if you find it useful.