In general SCSS files are CSS files with some special features. When i want to edit a *.sass file in my project i noticed that IntelliJ knows that file type but there is no code completion at all. I know IntelliJ has code completion for CSS files.
Just going to "IDE Settings" / "File Types" / "Cascading style sheets" and adding ".sass" and ".scss" to it, brings auto completion to this file for normal CSS.
Is there a way to enable (add) all the special features of sass to the IntelliJ auto completion for functions like "lighten()" etc., too?
There are several tickets related to this in the JetBrains issue tracker, this one for example. Fortunately, it seems they plan on fixing it soon though.