💡Dim Already Watched Video Thumbnails

⚬ PROBLEM: I have a very bad memory and I just watch a lot of content on youtube. Sometimes I forget which videos I've already watched, or I wouldn't recognise the thumbnail/title.

⚬ SOLUTION: Darken/fade/dim already watched video thumbnails! The feature should include a customisation on how darkened/fadened/dimmed it is. This would make a clean and clear solution to my problem.

⚬ ALTERNATIVES: There's another extension, "Tweaks for Youtube", that includes this feature. Unfortunately, the extension doesn't have as many features as this extension. However, it is the feature I miss the most. I know I can turn off already watched videos using this extension, but I don't want to completely remove watched videos, just easily and cleanly identify them.

⚬ RELEVANCE / SCOPE: Personally, it would be a life saver, especially because of my ADHD. People with ADHD often get overwhelmed by choices, have memory issues, and enjoy watching comfort content (so completely hiding watched videos wouldn't be a solution).

⚬ "SIDE EFFECTS":

It might mess up themes, depending on if you choose to either fading it or darkening it.

⚬ CONTEXT:
//
Thank you!

SHORT Table	(Summary)
Problem	bad memory makes it harder to identify watched videos
Solution	dim or fade watched video thumbnails
Alternatives	"Tweaks for YouTube" extension or hide watched videos
Scope	very helpful for people easily overwhelmed/people with ADHD
Side effects	might be in conflict with specific themes
Context

No files, tests, or entry points are named. Start by finding how the extension identifies watched videos and styles their thumbnails; then confirm the dimming control, theme behavior, and watched-state appearance before considering the work complete.