If you don't want Approvers to see where an expense gets allocated to because you don’t want to confuse them, you can use the following solution:
Account Codes can be set as optional in the Requester matrix.
Then, Requesters don't need to specify an Account during Purchase Order creation.
So, Approvers won't see which Account is relevant here when they make their approval decision.
After the final approval, the responsible person in Xero can add the correct Account.
Any Changes will be synced to ApprovalMax.