ETL : Mapping entities/ transformation Rules

Hello OneStream community,I'm working on a data import process where our source file contains Entity codes with hyphens (e.g., "ENT-BER"), but in our OneStream application, these codes use underscores instead (e.g., "ENT_BER").I'm looking for an efficient way to automatically transform these Entity codes during the import process without having to create individual mappings for each entity.

Where in the OneStream configuration should I add this transformation rule? In the Data Source settings, Transformation Rules, or somewhere else?

Any guidance or examples would be greatly appreciated. Thank you in advance for your help!