This tool uses native UNIX sort command to order VCF dataset in coordinate order. For technically inclined the command is:

(grep ^"#" INPUT_file ; grep -v ^"#" INPUT_file | LC_ALL=C sort -k1,1 -k2,2n -V) > OUTPUT_file

The same result can be achieved with the Galaxy's general purpose sort tool (in this case sort on the first and the second column in ascending order).