Greasy Fork

Great script - works on subscription page, main page, searches etc.
But it doesn't overlay on the sidebars when playing an actual video
(ie:https://www.youtube.com/watch?v=)
Anyway for this to be fixed?

What do you mean? It works for me.

The script should return the "watched" badge anywhere the red bar appears on the thumbnail.
If youtube doesn't display the red bar then the script won't work there. Blame youtube.

Then I'll blame youtube, as the red bar is also missing from the sidebar on watching pages, at least for me.

Ah yes, the related videos. The red bar is missing, I remember it used to show up there but not anymore apparently.
I'm guessing they did it so you'd have to click and watch the same video again, double the watch time, double the ad money. Though I very rarely look at the related videos.

Yes, the related video section. It was showing red bars until very recently, within the last month or two.
Guess I'll search out a way to hide viewed videos in the related section (as I don't want them hidden 100%).

Changing rating from Ok to Good as the issue is with Youtube and not your script itself.

After a year seems like Youtube finally fixed the watched progress marks for the related videos.

Fantastic - thanks for the update!

Noticed that when I use the pinned player from Nova (https://greasyfork.org/en/scripts/433360-nova-youtube), this script overlays certain elements - is there any way to fix this?

Managed to brute force it within Nova by changing
z-index': 'var(--zIndex)'
to
z-index': '1005'
(which is above your top z-index of 1003)

Hopefully this doesn't lead to complications further down the road...

You can try lowering the z-index in this script instead of forcing a z-index in nova youtube.
I think 11, 12, 13, instead of 1001, 1002, 1003 should work. Maybe even lower values like 1,2,3.
Can you try it and let me know?

Yes, that worked - I reverted to original VAR for Nova and changed your z-index values to 11, 12 and 13 - works great.
Didn't want to go as low as 1,2,3 in case any other scripts I have interfere.
Thanks again.

Thanks for confirming.
I've updated the style with the smaller z-index