Have not tested it yet (for some reason the itch download did not work at the moment) but was wondering if you can upload multiple builds at the same time?
I personally use batch file that uploads a win version, when it's done a mac version and after that a linux version.

Currently it just supports a single build at a time. It could probably be reworked to support multiple though? I didn't really give that much focus while working on it.

Okay. That's a feature I would like. ;)
(But just a suggestion)