The document selector used to have a horizontal scroll bar. It seems to have vanished. This was useful when displaying full paths -- usually the 'interesting' part is at the right end of the path. With a large development tree (e.g. in a website framework) the paths are often very long.
Sorry, yes, by "used to" I meant in the old TP4 days. It was a useful feature, and I was surprised it disappeared in TP5. I keep looking for a missed option somewhere that turns a scrollbar on.