Once a Layout Editor has uploaded Galleys, the OJS processes the file into the format to be displayed by the system. The original HTML remains with the Layout Editor.
Sometimes, however, another person may need to edit that HTML later on, for example to correct an error after proofreading when the original Layout Editor is unavailable.
However, if you download the HTML from the journal site, it is not an exact copy of the galleys, making it very difficult to edit.
I recommend that the original galleys, exactly as submitted by the Layout Editor, be accessible for download on the Editing screen.