Agents and managers cannot create knowledge articles from Community questions.

The ownership group for this knowledge article. An ownership group consists of a group of members and a manager who are responsible for approvals, ensuring article quality, and feedback tasks. Ownership groups can publish, edit, and retire knowledge articles that they are associated with.
Reference: https://docs.servicenow.com/bundle/orlando-servicenowplatform/page/product/knowledgemanagement/task/create-knowledge-article.html