Apart from being useful for statistical purposes, this function is the only way to know the name of the document currently being translated in a project (the numbering on top of the segment list rarely helps identify a document, because the order created by CafeTran is not the same as the one on the computer - Finder for Mac, in my case).
Every time I change segment, the statistic reverts back to "Project statistics" and I have to keep selecting the option "Current document statistics". Maybe it would be possible to have both Project AND Current document statistics separated horizontally or vertically?
I don't know if what you suggest will be implemented, but whenever I what to know which document I'm working in (in a multiple files project), I just press Ctlr+D or the Documents button (or Project > Documents). On a Mac, the actual shortcut can ne slightly different.
This shows you the document you're in and lets you quickly jump to another one as needed!