Hello Bill Tong,
You can't access the ID of objects in that way. If you want to retrieve the GUID of the Task, you can use the getGUID Java-action from Community Commons to do so.
Hi Bill,
You can also try this way to enduser click on the link in email to complete that task.
Create one microflow for deeplink in that flow call Task inbox page.
In DeepLink.DeepLinkConfig -create one deeplink call this microflow.
In email you should send deeplink url to the enduser.
If enduser click the link the deeplink will trigger to show the task inbox.
In that page it will show the currentuser task to complete.
Thanks,
Arun
my page URL setting as the following screenshot