PlaceholderExecutable/executorCell.jelly, which shows steps being run on a particular slave (executor slot), currently only shows something like Building myflow #99. It would be nice if it showed which stage (StageAction) the build was in.

(The StageAction Javadoc leaves open the possibility of stages which are thread-specific. But the StageAction attached by StageStep is not thread-specific, so this refinement is not important.)

More broadly, and to support parallel threads better, find the nearest ancestor of the FlowNode available to the PlaceholderExecutable which has an attached LabelAction, and display that label.