Yes, you can push updates of the workflow out to in-progress checklists.
If you started a checklist run using a workflow, but noticed there is a step missing, you can update the workflow and that will add the changes to the checklist run. This works if you’re adding steps, changing title/description, removing steps, changing the order, whatever.
Simply go to the worklows page and edit the workflow. When you’re making changes to the workflow, you’ll see a blue button on the top of the page to update in-progress checklists.