No, no popup involved. SU-4 is just a mode, an optical slave. It is not in the TTL/Manual mode menu, but is sort of standalone mode like Remote for Commander is standalone (not in TTL/Manual menu).
Just put it in SU-4 mode, and set a SU-4 manual power level, and just set it out there. SU-4 mode is an optical slave trigger that will trigger in sync, same as any studio light works with their optical slave trigger.
Commander has issues triggering a hidden flash, but a Commander slave is triggered with the lowest possible power level of flash (to leave something for the next working flash).
SU-4 mode is a less complex trigger (any simple flash, instead of binary encoded data stream), and it is triggered from the full working power of the other flashes involved (your Bowen). It easily works without concern about positioning its sensor in any normal room I've used it in. If extreme distance (like 100 feet), you probably have to aim the sensor at the trigger. If greater distance, I suppose some issue could be possible? But in any normal portrait setup, it has always worked great in every case in any normal room, without concern. There is enough wall reflections to easily handle it.