and then just eval it to get new functionality? And the various implementations I linked to here are trivial to figure out and write yourself with even the most passing familiarity with Emacs Lisp. Even if you're a complete newcomer to the language, Emacs is self-documenting and can teach you everything from inside the editor.
https://www.emacswiki.org/emacs/CopyingWholeLines#toc3
and then just eval it to get new functionality? And the various implementations I linked to here are trivial to figure out and write yourself with even the most passing familiarity with Emacs Lisp. Even if you're a complete newcomer to the language, Emacs is self-documenting and can teach you everything from inside the editor.