I'd love to see a second encounter marker for planets / moons when setting a maneuver node. At the moment the game only gives a second encounter for other spacecraft. Without a second encounter, outer planets like Jool and Eeloo can be a real pain to trial and error.
For example, let's shoot for Jool, but we missed our injection.
With only the 1st encounter visible, as it is in the stock game, only the closest encounter will be shown. In this scenario no matter how Prograde you go at the Apoapsis you'll never be shown intersecting as it only shows Jool's 1st encounter being right in front of you. If your lucky you can check a few orbits down the line to see if you get close using the maneuver node but 90% of the time doing anything from the Apoapsis won't get you any results.
You would have to check future orbits and burn Prograde at the Periapsis which means you'll have to use more fuel slowing down once you actually get there. And even then the game gets real glitchy as the marker slides wildly around, faster and faster as it jumps from the first and second encounter, showing you neither. That's not even mentioning the 10+ minutes of max time-warp to get to that future node, but I digress.
By just adding a second encounter marker this becomes no problem! Just go Prograde at the Apoapsis until the 2nd encounter marker shows you intersecting. Something that would look like this!
For the record though there is an in-game work around by setting a second maneuver node ahead of the closest encounter then adjusting the 1st maneuver node before the encounter to see where the second encounter will be.
But for someone just starting the game it could be literally hundreds of hours of gameplay before they figure this trick out. Believe me, that's coming from experience! XD
A second encounter marker for Planets and Moons in the base-game would make interplanetary travel much simpler! No maneuver node tricks or mods necessary!