Difficult in creating Parent Child Hierarchy Issue

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Hi
We are facing some issues with the client where we have had to hardcode lot of members, as parent child hierarchy method was not feasible.
For ex: by creating parent child relationship, we can directly tag the parent in rules and reports, which will automatically capture the child members. For my previous implementation which were using Oracle ERP, we used that and maintenance was easy.

However current client ERP is SAP, and there are no parent child relationship, and we are also unable to create parent child due to its complexities in its structure.