Recommendations To avoid maintenance efforts when more hierarchies are published, it is recommended for you to follow these recommendations: Create two tree versions of the same tree before creating any financial reports or allocations to force the fully qualified name to be generated.
Keep the two tree versions in sync always to guarantee fully qualified names are used in financial reports and allocations. Use the same tree version names over time to avoid breaking your reports or configurations. Use different hierarchies if you have requirements to roll the same child to more than one parent. The initial configuration steps must be completed before the definition of any financial reports, allocation rules, or Smart View queries
https://docs.oracle.com/en/cloud/saas/financials/20b/faigl/financial-structures.html#FAIGL777254

Cross Validation Rules: Overview
In Oracle Fusion General Ledger, use cross validation rules to determine the account combinations that are created dynamically as your users enter transactions or journal entries. Once enabled, a cross validation rule determines whether a selected value for a particular segment of the account combination can be combined with specific values in the other segments to form a new account combination.
A cross validation rule is defined in terms of a condition filter and a validation filter.
The condition filter describes the event under which the rule will be evaluated. If the event specified in the condition filter is not applicable, then the rule will not be evaluated even if it is enabled.
When the event specified in the condition filter is applicable, the validation filter condition must be satisfied before the account combination can be created. The rule is evaluated using the following logic:
If condition is satisfied, then perform specified validations.
For example, if your organization has determined that a certain company value, Operations, cannot use a specific cost center, Marketing, define the following cross validation rule to validate your accounts accordingly: If company is equal to Operations, then validate that cost center is not equal to Marketing.
If account combinations already exist and violate the newly enabled cross validation rules, these account combinations continue to be valid. Before disabling any existing account combinations that violate your rules and you are no longer using, move the balances in those accounts to the correct accounts. Then disable the account combinations manually to prevent further posting.
https://docs.oracle.com/cd/E28271_01/fusionapps.1111/e20375/F350915AN2814A.htm