The Custom JS Plugin for the Grav CMS allows to add additional JavaScript to your site, without editing the theme or having to create a plugin for the simple task of adding some custom lines of JavaScript.
Adds some custom JavaScript to your Grav site.
Open the plugin preferences in the Admin panel, and add custom JavaScript directly in the editor, which will be added as inline JavaScript in the heads of the pages, or enter one or more paths to load. (e.g. /user/my_js/custom.js)