Менеджер загрузок (S3) - это дополнение к браузеру Firefox , которое поможет вам контролировать свои Загрузки
Это новая жизнь для старого известного дополнения Download Statusbar , которое, в связи с критическими изменениями в Firefox 26+, перестало работать
https://addons.mozilla.org/en-US/developers/addon/submit/upload-unlisted
to get it signed because FF 48+ don't support unsigned add-ons (at all, not even with any about:config settings or .js files etc that I've tried so far) - but that site doesn't sign legacy add-ons anymore because it seems that Mozilla only wants to auto-sign those add-ons supported by FF 57+.
I might try installing CAA with PM/WF etc when I get back home, so maybe I could then install the older version of your add-on and copy it back to my Firefox.
All things considered though, it would be much easier if you yourself (or someone else who still has the .xpi file for 4.13) could just upload it somewhere. The traffic wouldn't kill anyone.