Review for DownThemAll! by Pinky Chuckles
Rated 5 out of 5 stars
I notice in about:config you can search for "extensions.dta" and see preferences for DTA. For example, I believe extensions.dta.ntask is for setting how many downloads at the same time.
Hope this helps, because DTA is broken and won't save settings anymore.
To create your own collections, you must have a Mozilla Add-ons account.