Toolkit for YouTube with 130+ options accessible via settings panels. Key features include: tab view, playback speed control, video quality selection, export transcripts, prevent autoplay, hide Shorts, disable play-on-hover, square design, auto-theater mode, number of videos per row, display remaining time adjusted for playback speed and SponsorBlock segments, persistent progress bar with chapter markers and SponsorBlock support, modify or hide various UI elements, and much more.
This script is great and makes YouTube not an eyesore, but it lacks customization features/settings. For example, I can't remove the explore more topics thing. The settings menu is also a little hard to navigate, mostly because the AI stuff feels like the main focus instead of just opening to the settings. This should just be a separate script for the UI improvements and a different one for the AI stuff. If I needed to use the AI stuff, I would install something specifically to add it.
You should also add theme features like this extension https://chromewebstore.google.com/detail/iedffooliepgabiihipcbokboecnfcbe and add an option to change to every major change the youtube ui theme has made, like this one, for example https://web.archive.org/web/20220501000031/https://www.youtube.com/, which is the best the youtube ui will ever be imo.