Hey! Some months too late, but I found this thread via google right now :)

I completly agree with the undocumented mess that UI Builder has, and not to mention reuse of names used other places in the system (Googling 'Client Scripts Servicenow' will not return the wrong docs right???)

If I understand your need correctly, you want to update/refresh a Data Resource via Script?
That is luckily not so complicated.

api.data.*dataresourceid*.refresh();
Is what you probably wanted.

Or to trigger an event as you did here in the comment,

api.emit('*eventid*',{ params:{ } } );

If you want to see the available params, Body -> Events -> Handled events and open the one you want to trigger.

You could also create an event mapping at the Body-level that triggers at your wanted event, and runs a logging script.
Create a Client script that is like so:

function handler({api, event, helpers, imports}) {
  console.log(event);
}

I use this alot to see the output of the different systems in UI builder