chouffainet Is there a way to add SEO capabilities to each file for ex. ?
For now, no. In fact, we even have <meta name="robots" content="noindex, nofollow"> in the header to prevent search robots from trying to scrape the content. It wouldn't come up with anything useful anyway, because there really isn't any page text content, just <title>foldername</title> and some files, and it certainly wouldn't display nicely in search.
It's possible I might extend SEO options, but this would require storing a _files.json data file inside the folder, where we could store things like title, description and anything else folder-related that could output into SEO meta tags. This effectively makes Files Gallery more like a CMS (content management system), perhaps something for the future.
When you say "to each file", I don't know what that means, because there certainly won't be any per-file SEO. Unless you are speaking of for example "image search"? Folder views in Files Gallery will count as pages for Google, but not individual files or images.
For now, you could remove <meta name="robots" content="noindex, nofollow"> in index.php and Google will index the website as usual. SEO impact will be minimal, because the pages don't have any text to index. Ultimately, Files Gallery is a file browser, not a website.