Jo Ator has a new video out where she goes by SkyLine from Terminal 2 (Concourse D and E) to Terminal 1 (Concourse B). Unfortunately, she gets off the train at the B station. Had she stayed on the train, she would have discovered that there is another station above the A/Z gates.
The map of the airport is accessible from this page on their website (download the "Terminal Map"). On Level 4. you will see all four of the SkyLine stations - D/E, C, B, and A/Z. The video I referenced in the previous post shows someone using the SkyLine before the C gates were closed, and you can see the SkyLine stopping at all four stations (although the doors for the Landside wagon don't open at C). You will also hear them announcing that all passengers going to Terminal 1 with luggage to check should get off at the B station, since it has direct access to the departure hall and the check-in counters.
Now, realistically, the other two SkyLine gates at Terminal 1 are of relatively lower usefulness for Landside (Public side) visitors. First, the station above the C gates, only serves the airside wagon of the SkyLine. That station was only opened in 2017, and, since the C gates are currently not being used, the SkyLine trains pass by it without stopping.
Second, going to the A station undoubtedly means going from the station, through security, into the A concourse, and then leaving the A concourse to anywhere else, like the departure halls, when you could just get off at B and go down the stairs into the hall.
However, for people arriving at an outside Schengen gate and departing from an outside Schengen gate in another concourse without a Schengen visa, the four airside stations (which are also outside Schengen, in the "transit zone") are essential to being able to get between concourses. There would be no way to get off the SkyLine at the B station and go over to the Z concourse without entering Schengen.
If there is no security between the airside SkyLine wagon and the airside gates of a concourse, someone arriving (for instance) on a flight from outside Schengen and going, with a short connection time, to an inside Schengen gate should stay in the transit zone until they get to their departure concourse and then go through imigration into the Schengen airside zone of that gate, thus avoiding the extra time of security.
So for someone arriving on Lufthansa from the US at a Z gate and departing for a Schengen zone airport from Concourse D, don't go through immigration from Z to A, then leave security to go to the departure hall and take the landside SkyLine to D, where you would have to go through security to get back to airside and your gate, just go up to the Skyline Z station and go to the airside D station, then enter Schengen in Terminal 2 and go to your D gate.