Add the extension properties by default and disable certain fields in the properties panel


I am looking for suggestions on couple of things here:

I need to use the Service Task. The properties in General tab needs to be autopopulated and disabled by default.
Also, I need to be able to add the names of the extension elements under the extension properties. The value should either be a drop down or a text field depending on the extension property.

Is there a way we can do it? I have been playing around with CustomRules,bpmnModeler events and other things. I cannot seem to make any progress.

Thanks in advance.

I got adding the extension elements part working with the below code (we are using camunda).
implementation uses custom palette.

const businessObject = bpmnFactory.create('bpmn:ServiceTask');
businessObject.extensionElements = bpmnFactory.create('bpmn:ExtensionElements');
var camundaProps = bpmnFactory.create('camunda:Properties');
var property= bpmnFactory.create('camunda:Property'); = 'name';

Yet to figure out how to disable editing the fields in the properties panel.