This functionality is built into Twitch.
It’s not a “third party thing” hence not in the docs
See this help document for information on this
https://help.twitch.tv/s/article/video-on-demand?language=en_US
Specifically “Export”
Your Twitch account can be connected to a YouTube account via your Connections page. Once your accounts are connected, you can use the Export option to upload your videos to YouTube directly from Twitch without having to download them locally.
Additioanally first party feature requests should go to the uservoice https://twitch.uservoice.com/ but this is already implementated anyway