Just make a debug with search term.

debug:container --show-private workflow

this would be the result:

Select one of the following services to display its information:
  [0] console.command.workflow_dump
  [1] workflow.abstract
  [2] workflow.marking_store.multiple_state
  [3] workflow.marking_store.single_state
  [4] workflow.registry
  [5] workflow.security.expression_language
  [6] workflow.blog_publishing
  [7] workflow.blog_publishing.definition
  [8] workflow.twig_extension
  [9] Symfony\Component\Workflow\Registry

The above is a simple and a not usable result for your bussiness logic.

If your intention is to do “something” with the output, take a look at the Symfony\Bundle\FrameworkBundle\Command\ContainerDebugCommand and try to extend the command and implement your own logic.

If you extend(which I recommend) the Command you will have access to the getContainerBuilder function which gets you the builder container and then you can do $builder→getServiceIds() and start a string search inside a loop returning all the matched services and that would be your workflow list.

Hope it helps!