A tool I use constantly in frontend development, and it works perfectly in combination with WeBuilder.
Prepros App offers compilation support for Less, Sass, Stylus, Markdown and more.
Some of the other notable features in Prepros are live browser refresh, Image optimization, built-in server, multi-device testing and FTP support for deployment.
It also allows the ability to create shareable configuration files which is useful when working in a team.
Runs on Windows, Mac and Linux.
https://www.prepros.io/