Live editing SCSS files in Chrome DevTools with Prepros

Question

I just started using Prepros to compile my SCSS files and I can't seem to figure out how to enable live editing of those files in Chrome Developer Tools.

I'm not really sure how this is supported nowadays, but I've found some examples showing this in action (such as this video) and I know it used to be an experimental feature in earlier versions of Chrome.

In Prepros, I have Source Map enabled and the map is showing up in my filesystem properly.

Chrome is also showing all the SCSS files correctly, but I can't save any changes to the file system (basically, whenever I change something, it only changes in the compiled main.css file).

As you can see here, there are no green dots next to the SCSS files:

...and when I try to edit and save them in the Sources panel, this shows up:

Here's my Prepros project structure (everything gets compiled into the main.css file):

Is there any way to set this up so that I could edit anything in DevTools and save it to the file system from there? I want to avoid copying code over to my text editor as much as possible.