Community owners can manually curate content appearing in their widgets by highlighting them (Documents, Ideas, Blogs, Questions and Wikis).
For example, a document can be highlighted in two ways:
1. from the Files section.
2. from the startpage and community newsfeed.
Please note that files in Updates(aka Posts) cannot be highlighted from the newsfeed.
All the other content is not yet available for highlighting (Post, Praises, Tasks, Polls, Forum and Events).