Service Desk Help is the reader. The article library is where the articles are created. A draft does not appear for readers.
Who sees what
The help centre for agents is at /app/knowledgebase/help. It searches and browses published service desk articles. The landing page that opens that browse is /app/knowledgebase/help-center.
Show in Customer Portal, on a published article, is what makes that article available to portal customers. Leave it off and the article stays with agents. Publishing can also be connected to a workflow and a status flow under Workflows & Status, at /app/knowledgebase/integrations. The workflow designer and the status flow designer are in Service Management configuration.