For that you need to create a mark point. They are lettered, instead of numbered, from A to Y (Z is usually overwritten but a markpoint set to where-ever you drop a bomb or launch a missile.
I can't remember off hand which button it is but I think it might be TMS right long? Then you need to set the CDU to Mark Point mode. If you make the HUD SOI, you can cycle through them like waypoints. If you use the TAD, setting the CDU to Mark Point mode removes the waypoints displayed on the TAD and it instead shows Mark Points. You can easily slew your cursor over one and make it the SPI again.