I'm using CubeMX v6.11.0 to generate code for STM32G474.
When I change TIM20's "Request Number" from the default 1 to 4 and press "CTRL + S" to save or click "GENERATE CODE", the number always changes back to 1 automatically.
I've been able to set the Request number to 4 then saving the project. After closing and reopening again, everything works fine on my side (Request number is kept on 4):