You can access to the workflow Service Health on this page >>> "/_layouts/15/WorkflowServiceHealth.aspx" , and you will see the current status including the workflow queue length.
Then you will see a table with the columns:
- Workflow name
- Started
- Suspended
- Canceled
- Terminated
- Completed
- Total
, showing the number of those status
Also you can click on the information button
and will see Details of this specific workflow, showing the Most recent update and also a link to Terminate all instances of the workflow.