We have developed an extension for Visual Studio Code that provides syntax highlighting for Cylc files. It’s available at the Visual Studio Marketplace which can be accessed at marketplace.visualstudio.com/items?itemName=cylc.vscode-cylc or from within VSCode by searching for “cylc” in the extensions panel. Note currently the minimum supported version of VSCode is v1.41.0; if you’re using an earlier version let us know as we can probably support it.
For the other editors, a TextMate bundle is available at github.com/cylc/Cylc.tmbundle - follow the corresponding installation instructions there.
A package for Atom is also in the pipeline.