They are called softkeys because they activate at different times. For example the SUSP (if memory serves me right) appears when flying an IAP, and when you go missed approach the MAProcedure is suspended until you press the softkey. Pressing the softkey enables the MAP.
VNAV appears when flying a GPS approach and vertical guidance is available but not LPV. If LPV is available then that will appear instead.
The best thing you could do is experiment either in the air or in a proper sim.