Review for Preserve Download Modification Timestamp by cy1
Rated 4 out of 5 stars
They changed the interface to downloads, only exposing the Referrer header to javascript code, and only exposing the string path, not the File object of the target to javascript code. So it looks like they're actively trying to stop add-on developers from modifying the download based on HTTP headers like Last-Modified. Sigh...
To create your own collections, you must have a Mozilla Add-ons account.