Feat Req for PL manager: Add a delete all fully watched vids, leaving partially watched undeleted

[jsburwell]

Add a delete all fully watched vids, leaving partially watched undeleted. Perhaps allow user to specify what qualifies as "fully watched", 50%, 90%, etc.

Sometimes you just want to clear the fully watched videos from the top for your Watch Later without deleting that last video that you only watched part of and want to continue...

[NabokD]

Thank you for sharing!