It's possible to use Tamper Monkey to do this, without modifying your Moodle site. TamperMonkey is a plug-in for browsers that can run JavaScript on certain pages (the @match configuration).
Here's the relevant code (I don't have old versions of Moodle to test this on, but it works for me):
// ==UserScript== // @name Moodle collapse review panel in grading // @namespace https://profs.etsmtl.ca/cfuhrman/ // @version 0.1 // @description Save many clicks by collapsing the PDF review panel in grading // @author Christopher Fuhrman // @match https://*/mod/assign/view.php*action=grader* // @require https://code.jquery.com/jquery-latest.js // @grant none // ==/UserScript== // Note: the "action=grader" in the @match above is the 3.x grading interface, so this won't be invoked on older versions of Moodle (function() { 'use strict'; $('button.collapse-none').removeClass('active'); $('button.collapse-review-panel').addClass('active'); $('[data-region=review-panel]').addClass('collapsed'); })();