Access Request Decision trigger for external access requests

When access requests are made from ServiceNow and the flag for approvalsMustBeExternal is set to true, the Access Requesst Decision trigger does not get invoked, is there any way to kick off a workflow when access request is submitted from ServiceNow

This seems by design and kind of obvious. You can overcome this by calling idn workflows from snow workflows using api.

Per @chirag_patel 's suggestion, you can use the “External Trigger” in your workflow. This will generate an endpoint that will allow your ServiceNow workflow to invoke the trigger anytime an access request is made.