A check mark   denotes a executed step which has checkpoint defined and you can revert to the step after executing workflow.

A check mark with a hash   denotes a step that is reversible after executed.

A question mark   denotes a step that is blocked that needs input from previous step’s outcome or user-defined values.

A lightning bolt   indicates that the step is ready to be executed.

A red exclamation mark   denotes that the operation is blocked due to an error during execution.