Currently there are at least 4 places in core (Course, SMS, Communication & AI) that fire a JS event when a select box in an admin form is changed. Typically this fires an update button action for the form that allows a hook to add additional fields to the form.

For example: https://github.com/moodle/moodle/blob/main/sms/amd/src/smsgatewaychooser.js

Each of the instances implement copy paste versions of the same code. These should all be refactored into one core instance (perhaps as a new mform field type).