ToolJig is an HTML/CSS/Javascript application that enables researchers to create Common Workflow Language (CWL) tool and workflow descriptions in an interactive manner. You can read more about ToolJig and the motivations behind it in our journal article, Simplifying the development of portable, scalable, and reproducible workflows.
You can use the app for building CWL tools here.
You can use the app for building CWL workflows here.
You can see example CWL documents in the examples directory.