To avoid any mistake, before deleting a workflow you have to deactivate a workflow.
Follow these steps to delete a workflow in your workspace-
Mouse hover on your profile image at the bottom left corner and click on 'Workspace settings'. The URL will look like this https://yourdomain.goodflow.io/settings - and you can see all your workflows there.
In workspace settings click on Workflows, there you can see list of your workflows. Click on 'deactivate'.
After deactivating you will get the option to delete them.