As of writing this we don’t yet know how the wrecked Death Star is going to factor into Episode IX, but I had some thoughts related to the Death Star that could help tie the trilogies together.
In a few of the scenes in the Emperor’s throne room in ROTJ, we see a big screen to the right of the Emperor’s throne. In some scenes, though, there isn’t even anything displaying on the screen, it’s just blank. Maybe something could be added to the screen that could tie into Palpatine’s Contingency, the First Order, Snoke, or something else that is relevant in Episode IX.
Also, there is one scene where Vader goes to see Palpatine, and he is initially turned around in his throne looking out the window. Something else could be added to this scene, like a hologram that Palpatine could be looking at instead, which Palpatine dismisses when Vader approaches him.
These things don’t have to be anything major, just subtle clues, but these little details could be used to chronologically foreshadow elements in the ST for a nice marathon viewing of the saga.