Moodle-3.3 has a new HTML_QuickForm element type called defaultcustom, which displays a checkbox right above the text input field, to indicate if the input field value should remain with it's default value, or can accept customized value.
php implementation for this element type is in ./lib/form/defaultcustom.php
It is used in course/editsection_form.php line 27,
so when creating a new section in a course, which gets a sequential name by default (e.g. Section-123), can be overridden with a custom name.
By default this checkbox is not checked - meaning that the user can save the section without changing the section name. (see the attached screenshot).
We would like to have this checkbox checked by default, in order to encourage (or actually force) the user to fill in a proper name, and not leave the default name as is.
I couldn't find any documentation on this new element type, not could I figure out how to force this when creating the element.