This plugin adds a checkbox to the YouTube Subscription Feed that allows users to toggle whether or not they want watched videos to show up in the feed. The aim of this is to make navigating the subscription feed much easier and intuitive. Current features:

Hide videos that are marked as WATCHED in Subscription feed, YT Home and Channel Videos page
Mark videos as WATCHED to hide them from feed
Mark all as WATCHED
Hide videos in subscription feed automatically, once you start watching them
Hide Premieres until they are available to watch
Hide Shorts
Hide empty sections (Today, Yesterday, Last Week, etc)
Collapse sections to navigate to older videos more easily
Show videos that have been hidden
When hidden videos are shown, unmark videos as WATCHED to show them in feed again
Settings page with configurable options

If you find any bugs or want to request new features, or if you want to contribute to the project, you're more than welcome to do so via Github: https://github.com/OsaSoft/youtube-better-subscriptions You can also reach out to me via Twitter: https://twitter.com/Osa_Soft For full changelog check see the extension install/update page or on GitHub. Also available for Chrome: https://chrome.google.com/webstore/detail/better-subscriptions-for/fkchdogohkjpnhfkganifkbbjcjofbjf