Fallback approver for attestation

Should be possible, but I haven't tried it yet.

What version are you using?

Version 8.1, not seems to be useful, In manager view pending approver shows as fallback approver but when I login to portal it shown nothing pending.

Also irrespective of approval procedure , fallback approver is showing as approver for all the attestation policies in Manager view when click on approval sequence task

I believe the thing is that you are mixing things up here with the role assignment.

The fallback approvers are used if attestation cases cannot be approved because no (regular) attestors are available. An attestation case is then always assigned to the fallback approver for attestation if no attestor can be found in an approval step in the specified approval procedure.

The chief approval team can approve any approval step and is used if a determined (regular) approver is unable to approve. That's why you are seeing them as approvers in the Manager. The web portal separates the cases, that a user can decide just because he is a member of the chief approval team from the normal ones to avoid an overwhelming number of cases to decide for the end-user and to avoid that a chief approval team member is approving everything just because the case is coming up in the normal view.

That's why there is a special escalation menu item for these cases. https://support.oneidentity.com/es-es/technical-documents/identity-manager/8.1.1/web-portal-user-guide/39#TOPIC-1244494

By the way, there are many enhancements in regards to that topic in the service releases since 8.1.