Want to add custom attribute in bpmn:Task but I can't

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1

Hello Everyone,

I am trying to add a custom attribute to an existing bpmn element that is bpmn:Task it took me 3 days but still no success can you help me how can I do it
I’m using angular 15 and following is the approach I have used

@ViewChild('canvas') canvas: ElementRef;
modeler: BpmnModeler;


ngAfterViewInit(): void {
    this.modeler = new BpmnModeler({
        container: this.canvas.nativeElement,
        moddleExtensions: {
            custom: customDescriptor
        }

    });
    if (this.xml) {
        this.modeler.importXML(this.xml);
    } else {
        this.modeler.createDiagram();
    }

    const eventBus: any = this.modeler.get('eventBus');

    const events = [
        'element.dblclick',
    ];

    events.forEach((event) => {

        eventBus.on(event, (e) => {

            this.selectedActivity = e.element;

            if (this.selectedActivity.type == "bpmn:Task") {
                this.displayContractObjectForm();
                this.visible = true;
            }


        });
    })
}

updateModeler(xml: string) {
    this.xml = xml;
    this.modeler.importXML(xml);
}



handleObjectChangeActivity(event: ObjectChangeInformation) {

    const modeling: Modeling = this.modeler.get('modeling');
    const elementRegistry: any = this.modeler.get('elementRegistry');

    const taskElement = elementRegistry.get(this.selectedActivity.id);


    if (taskElement) {

        modeling.updateProperties(taskElement, {
            'custom:myCustomAttribute': 'Your Value Here'
        });

        this.modeler.saveXML({ format: true });
        console.log('xml =>', this.xml);

    } else {
        console.error('Task not found');
    }

}

the customDescriptor is as follow
{
“name”: “Custom”,
“uri”: “http://yourcompanyxyzavs.com/schema/bpmn/custom”,
“prefix”: “custom”,
“xml”: {
“tagAlias”: “lowerCase”
},
“types”: [
{
“name”: “ExtTask”,
“extends”: [
“bpmn:Task”
],
“properties”: [
{
“name”: “myCustomAttribute”,
“isAttr”: true,
“type”: “String”
}
]
}
],
“emumerations”: ,
“associations”:
}

I applied many ways but could not get any success

also took help from followign source