UPDATED 22.11.2022
It's been two years since the last update, so here's the updated working script as per the comments below.
Thanks to BryanHaley for this.
setInterval(function () {
video = document.getElementsByTagName('ytd-playlist-video-renderer')[0];
video.querySelector('#primary button[aria-label="Action menu"]').click();
var things = document.evaluate(
'//span[contains(text(),"Remove from")]',
document,
null,
XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
null
);
for (var i = 0; i < things.snapshotLength; i++)
{
things.snapshotItem(i).click();
}
}, 500);
Non-english users will need to change "Action menu" and "Remove from" to what YouTube uses for their localization.
This thread was a good reference when I need similar functionality (many thanks!), so I implemented it into a web extension. But my code was a little bare, and private extensions doesn't seem to be a thing, so just recently I converted it into a Userscript.
https://gist.github.com/AndersMoberg/0a9f996a49d7b3a9e9c01065ce29abf4
If you have a Userscript manager, press the Raw button and you should get the dialogue for installing it.
It only works with Swedish interface for now, but feel free to request your language if you'd like I can put it in.
Again, many thanks for this Gist and comment section