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Clicking on the star will mark a file as a favorite. You can find your favorite files with the favorites search located in the toolbar. Clicking on the name of a file will bring up the editor (for text files), preview images in a lightbox, or download binary files. By clicking the version number a version history dialog will appear providing a comprehensive record of how the file has changed over time.
For more information on the Version column and version history check out the tutorial See changes made to file using file manager version history