Sometimes it is useful to directly work with Jenkins model objects from a Workflow, such as the FilePath representing the workspace for the enclosing node block. Currently you cannot access these. It would be useful to have a Step which just gave access to a specified contextual object (given as a String class name I suppose). Typically you would need to run in whole-script approval mode, since relevant methods on such objects are not likely to be safe to whitelist for use from the sandbox.