Hi, I'm starting developing in Moodle 4, and I'm trying to custom the courses edit_form.php

I'm trying to add new fields to existing sections, for example, in the General section. This works, a new field appears, but the information added here is not saved, once the page is updated, all the other fields are changed, except this one.

The code I added in core/course/edit_form.php:

    $rootpath = get_config('repository_pluginname', 'rootpath');

    $mform->addElement('text', 'rootpath', get_string('rootpath', 'repository_pluginname'), array('size' => '40'));

    $mform->setDefault('rootpath', $rootpath);

On the other hand, right now I am trying to make these changes in the original file, but I would like to know if there is a way to make these changes in other files, for example, in files belonging to a plugin. I have tried to extend the class, but I have not been able to see any changes.