APM Policy Modern-Style: How to mark Text Bold or insert New-Line?

seem's like the modern template is more limited.

i used to replace the whole login page with my own html code, and that worked great.

with the new modern template that does not seem possible anymore.

for instance, i want to add some javascript function that gets run on the Onselect event.

therefor you need to be able to add the unselect event to the form.

so if anyone has an idea, let uw know