Ordering dowloads in queue

[dim6003]

Helo, new user here (Ubuntu 20.04). I have added some files from a site that allows only 2 downloads at a time, and with very low bandwidth. These files are pretty big (around 10 hours dl per file!), and are parts of some multi-part archives.
However XDM seem to pick them randomly in the queue, when I'd like to complete one set (multi-part archive) before staring the next one. how do I specify in which sequence the queue should be downloaded?

Thanks.
DM.