The basic steps to do that are:
get SIZE asize # takes the size of the current file
append # enable the append mode for concatenating them
log "new.bin" 0 SIZE
append # disable concatenation (not necessary if its there are no other operations)
With those few lines you have a script that you can use on all the files you want to concatenate.
For example when you launch quickbms with double-click, select this script, then select all the files you want to concatenate and then the output folder.
It should work very well, try it.
Otherwise I have a command-line tool called bincat