If you add a fiew files do download/upload list and you quit from Smbc before Smbc finished download/upload all files, then Smbc saves this list to file "~/.smbc/dulistX" where X is a first free number. If you do the same at one time with more that one Smbc in "~/.smbc/" directory will be created more that one "dufileX"; example:
dulist0 dulist1 dulist2
At some time you again run Smbc. Now Smbc is searching to "~/.smbc/" directory to files "dulistX" find and load a file with the smallest numer. If this instance of Smbc finishes download/upload all files it is searching again "~/.smbc/" directory and again load next found "dulistX" file.