Feature request: Deduplication of list items

[tsilvs]

Checklist

• I checked, but didn't find any duplicates (open OR closed) of this issue in the repo.
• I have read the contribution guidelines given at CONTRIBUTING.md.
• This issue contains only one feature request. I will open one issue for every feature I want to request.

Describe the feature you want

An option to automatically find and remove and/or disallow duplicate list items (for Youtube it would be videos in playlists).

Is your feature request related to a problem? Please describe it

I'm creating multiple lists by categories as I plan something to watch later. Sometimes the playlist accumulates quite a lot of videos so I don't remember if a video is already in a list or not.

Additional context

Duplicate Tabs Closer Firefox Extension is nice)

How will you/everyone benefit from this feature?

It will be much more convenient to use playlists.

[RickyM7]

I think it's a duplicate of the #4186.

[triallax]

To be more precise, it's a duplicate of #1473, which was closed in favor of #4186.