Limitations

Use of Entity Reference for Unique Keys Compatability with Power Automate

⛔ Below example will fail if used with power automate (not supported directly by power automate)

{
    "regardingobjectid": "{{ entityreference('contact', [{'emailaddress1','john@example.com'},{'lastname','doe'}]) }}"
}

Use of Source ID in Pre (Operation or Validation)

⛔ Exception will be thrown since the source was not operated yet

{
    "regardingobjectid": "{{ source.contactid }}",
    "regardingobjectidtype": "contact"
}

✅ However updates works fine

{
    "contactid": "{{ source.contactid }}"
}