This plugin aims to make navigating YouTube's subscription grid easier by allowing users to hide watched videos. This plugin is in early development and will often change and (hopefully) include new features.
Available for Firefox: https://addons.mozilla.org/cs/firefox/addon/youtube-better-subscriptions/
Available for Chrome: https://chrome.google.com/webstore/detail/better-subscriptions-for/fkchdogohkjpnhfkganifkbbjcjofbjf
The icon for the marked watched Button is based on: https://commons.wikimedia.org/wiki/File:OOjs_UI_icon_eye.svg published under the CC-BY-SA-3.0, the modified version is licensed under CC-BY-SA-4.0
The icon for the settings Button is taken based on: https://commons.wikimedia.org/wiki/File:OOjs_UI_icon_settings.svg published under the MIT licence, , the modified version is licensed under MIT
The addon as a whole is still licensed under the GPLv3