Awesome write up Eke Victor, I didn't know of Koala until now.
I'll like to add another way to set up SASS, if you don't mind. I think this is the only method that supports the latest version of Dart Sass, I'm not sure though. Here's how to set it up:
You could run the command on the terminal:
npm install -g sass
Then while starting a sass project, run npm install sass
Then in the package.json add the script:
"scripts": {
"sass": "sass --watch sass:css"
},
The script signifies that you're watching a folder named sass and then compiling to a folder named css.