Today we can narrow a search in FARR to folders only by adding "\" (backslash). Example: compare a search for "program" and "program\"
But on some keyboard layouts the backslash is tricky to reach. For instance, on my swedish keyboard I must press AltGr + (plus key) to get a backslash. Since the space bar is easy to reach on all keyboard layouts I've seen, why not let a double space do the same thing as the backslash currently does? Of course if the user has a lot of files with double spaces in their names then this idea would mean trouble. But I suspect file naming is extremely uncommon.edit:
alternatively, multiple spaces could be tied to some other function. For example, FARR could see any sequence of spaces that is even (2,4,6...) as identical as the +sall command, but see uneven number of spaces as a deactivation of that command. That way, the user could very quickly toggle the +sall functionality on and off. Other uses are possible also I guess but the double space sequence seems so quick and easy to remember that it should be used for something!