We are migrating to cloud and updating the old class structures to reduce the testing impact

In current implementation we have 2 case types and class structure is as of like below

UBank-Claim-Work-ABC

UBank-Claim-Work-DEF

DEF is a child case for ABC and the same is defined in case type rule. We are creating Child cases in flow with the case creation shape and this is fine

As part of Cloud class structure is changed and is define as below

UBank-Claim-Work-Test-ABC

UBank-Claim-Work-Test1-DEF

As the class structure is changed I am unable to define DEF in the case type rule of ABC and also unable to refer DEF in create case utility. But we need to create DEF case type from ABC and link it as a child case to ABC. (Note: I am able to create DEF via create case utility. But unable lo link as child case)

Any approaches please