I don't believe that Lowrance or any other Sonar manufacturer can do this.
It's true that you can record on both units to an SD card, then while viewing a recording, create new waypoints based on what's on the recording. So, in essence, you are reviewing the history and making waypoints from it. But ONLY if you have made a recording to an SD card.
To keep a real-time, ongoing cache of recent history is just
a plain waste of memory. I think these units barely have enough
memory to do what they were designed to do.
I disagree, when you add up all the options, Lowrance is more expensive than Humminbird.