How can I sort files found by Google search according to their size or show only results that are larger than x Kilobytes? For isntance using filetype:mbox to find only large .mbox files.
I suspect this is not supported. There's no evidence of it in the "advanced search", nor in the guide to search operators (which advises against worrying about memorizing all of the operators because you can use the advanced search page.)
Also, the advanced search help page lists filters and doesn't include file size.