Hi Miriam,
I'll try to help answer your questions:
1. The purpose of the microflow from section 8.2 is to retrieve all the policy objects in the database and associate them to the policyDoc object. The policyDoc object is the context object that will be used to actually export the data. This is defined in step 7 of the Export to excel tutorial.
2. This change action should only change that association, nothing else needs to be changed
3. This definitely isn't super clear in the documentation. You will need to execute both microflows. First the microflow in section 8.2, then the microflow in section 7. The simplest way to do this in my opinion would be to create a microflow that calls both of the defined microflows as sub-microflows.
For example, you could create a new microflow called ACT_ExportAllPolicyObjects_XLS. In this microflow, you would first call the microflow created in step 8.2 which should return a policyDoc object. Then you would call the microflow created in step 7, using the policyDoc object returned from the first sub-microflow as a parameter to pass in to the second sub-microflow. You could call the ACT_ExportAllPolicyObjects_XLS either from navigation or a button on a page and is should result in an xls file being created and downloaded with all the policy objects.
Let me know if this helped clear anything up!