[manfre]

Without a link to the userscript, your comment is not helpful.

[RJIb8RBYxzAMX9u]

Not quite what you asked for, but this is the bookmarklet I use:

  javascript:(() => { let v = window.location.href.split("/"); window.location = "https://www.youtube.com/watch?v=" + v[v.length - 1]; })();