This information can be obtained from workflowManager e.g. by calling getApprovalSchemaExecutionInformation (requires approval task OID).
It contains information about individual stages of approval:
- for the current stage and previous ones, we can provide exact information - see ApprovalStageExecutionRecordType:
- events related to the stage (showing decisions done and automated completion events),
- active work items (for current stage only),
- for future stages, we provide estimates - see ApprovalStageExecutionPreviewType:
- errorMessage (if anything went wrong during preview).