Sublime Text (https://www.sublimetext.com/) offers a cross-platform solution. It may be downloaded and evaluated for free; however, a license must be bought for continued use. Some Red plugins are available, such as Sublime-Red (https://github.com/Oldes/Sublime-Red) or Rebol-Red-Sublime (https://github.com/onetom/rebol-red-sublime). They offer nice syntax highlighting, code snippets, and an easy way to integrate a build system.
By far the best and most complete cross-platform option at this time is Visual Studio Code with the plugin (https://marketplace.visualstudio.com/items?itemName=red-auto.red) developed by the Red team. It has many functions, such as auto-completion, code snippets, and built-in documentation ...
