Hello Benjamin,
I do not think, all your requirements are something we can get Out of the box.
[quote user="Benjamin N."]If that is blank it should move forward to approval by the Department associated with the invoice.
- In this step there should be defined a first approver and a second approver defined per department (set up as roles)
[/quote]
You can make use of the conditional decision to define who approves based on the department.
[quote user="Benjamin N."]If there is a "Purchaser.order.orderer" it should be sent to the purchaser orderer as first approver and then the manager of the purchaser orderer as second approver.[/quote]
The hierarchy architecture that will pick the line manager is built on the workflow originator/ or the workflow owner. Hence, you can not get the manager of the PO order in the workflow engine.