Amazon Connect Outbound CCP Softphone Number Prefill

I have a pretty simple requirement to click on a phone number hyperlink and have my web-app open the AWS connect soft-phone dialer with the selected number, ready for the person to press the "call button"

I have enabled an AWS connect account and I am hosting a custom CCP site via an S3 bucket (as illustrated here)

My plan is to initiate a link to the CCP page and embed a URL Search Param "?number=04125412,customTag=helloWorld"

I have used this code on the CCP Page

Also, within the index page, I add some code to receive the input params:

 <script>
    var urlParams = new URLSearchParams(window.location.search);
    console.log(urlParams.get('number')); //the phone number for the dialer
    console.log(urlParams.get('customTag')); // the call notes for the CTR custom Attributes
 </script>

I Am struggling to understand how I can interact with A: the Dialer to pre-fill the number and B: to post custom attributes to the AWS contact record during the call.

Any help would be appreciated.

from Amazon Connect Outbound CCP Softphone Number Prefill