it is only possible to migrate the G0 available function modules(IP) to G0 MCU, then update the MCU configuration and pins map from L4 to G0 in your project as "How to use STM32CubeIDE to migrate a project from MCU1 to MCU2?", it will OK. but if the function module you have applied in L4 is not available in G0, it will can't be migrated to G0.