Preprocessors have been a big "thing" in web development; from server-side PHP to ES6 transpilers.  Outsystems doesn't support any out-of-the-box (yet), but since it supports adding JS and CSS, we are able to compile some preprocessed code and copy/paste the results.  For example, I used LESS for an Outsystems project that is in production right now.

My question for the community is: has anybody used any preprocessed CSS or JS code for their real-world Outsystems projects?  CoffeeScript?  SASS?  Would you like to tell us if that was ultimately helpful to your project or not?

One correction to the above: you can preprocess JS code by making it an unescaped expression with appropriate strings concatenated at runtime.

Personally I don't see any advantages of preprocessors like coffeescript, because the core of Outsystems isn;t javascript, but the tool itself.

The less/sass I would like to be implemented in a basic form inside outsystems.
A simple variable system to setup colors for example would be an enormous benefit.

I agree we need this kind variable to setup colors and etc.