This is a script for Drafts.
let len = draft.content.length;
// if needed, insert a new line at the end of draft
if (!draft.content.endsWith('\n'))
editor.setTextInRange(len, 0, '\n');
else
editor.setTextInRange(len, 0, '');
// activate is not required if the action is launched via a keyboard button
editor.activate();
Published in the Drafts directory.