The question doesn't explain the whole situation. I'm aware of the Workspaces and of SASS source-maps. I'm already able- from the Styles panel- to track the line in the scss file where the specific rule is that I want to change.
That in itself is already a huge achievement, but what would improve a lot my workflow would be being able to visualize the changes as I'm making them live, and have DevTools save them automatically. That way I could instantly adjust elements.
That already can be done in plain CSS. In fact, DevTools is already changing the css file instantly even with SASS running. The problem is that as soon as you modify the scss file again, SASS will recompile and the change in the css file that DevTools made will be lost.
An image is worth more than 1000 words, so:
Unfortunately I don't think there's a good answer to your question. There are some ways to convert CSS to SCSS, but they're not intended to be an ongoing process, just a one time conversion.
It's best to only have the conversion one way, if it were bidirectional there'd be a lot of 'what if' situations with collisions that would get really hairy. It isn't a feature I'd want to try to figure out :P
In my workflow, I make small adjustments in the styles inspector (like you are above) and when I'm happy I copy those values to my SCSS file and recompile/reload the page. I think it's about as good as it gets without getting into really strange (probably) unexplored territory.
Small note: Chrome isn't actually editing the CSS file when you change it in the style inspector, it's just making adjustments to the DOM temporarily as if the changes were made where you made them. That's why it's lost on reload.