I think the TO mode of the PDCS should drive the EPR and ASI speed bugs when ENGAGE is pressed. That's what manual2 says. Maybe with the speed bugs then showing a certain flap setting speed. Lets assume flaps 5, which should be commonly used. Since the engage feature currently doesn't work, this may lead to a lack of information, right you are. Or we're both missing the mode showing the speeds.  :o

The upcoming manual3 may help us as it might include some tables for the takeoff speeds. The 707 worked that way.