1. Ability to toggle whether or not a wing has vapor trails. I like to sometimes make wings out of several wing parts, but this means that you end up with a bunch of vapor trails, some of which coming out of things like the middle of a wing, which I find kind of annoying.
2. Optional cover for hydrogen tanks. While I think that the hydrogen tanks look fine sometimes, other times I wish that you could give them a cover to make them blend in with your other fuel tanks better. Looks odd when the bottom half of a rocket is smooth fuel tanks, while the top half is a truss with this bright yellow hydrogen tank in the middle.
3. A simulation to test designs. Something similar to the KRASH mod from the first game, allowing you to test designs before you launch the actual mission, such as spawning your lander on Duna to make sure it can actually reach orbit. Maybe make it where you must actually reach a location first before you can simulate it as well, like you can't simulate a ship landed on Duna till you have actually landed there for real.
4. An IVA with functional monitors like the mod Raster Prop Monitor.
5. Multiple suits to choose from like in the first game. I liked choosing different suits in the first game based off of my tech level, such as the vintage suit for starting out, and the default one for like mid tech. I do really like the new suit though.
6. Option to switch windows between see through and opaque. I like being able to see through the windows, but sometimes in certain builds you will end up with things like the cockpit clipping into other parts. This means that you can have times where when you look through the window the kerbal is halfway inside a fuel tank or something, which can look odd. So being able to switch the windows to opaque in the editor for these kinds of cases would be nice, even if not super important.
7. A mapping system like the Scansat mod. This could be used to find good landing spots, as well as good spots for colonization in the future.
8. The ability to remove an item from symmetry so that way you can have items placed symmetrically but with different settings, such as navigation lights.
9. The ability to load craft from other save files like you could in KSP 1, Maybe even folders to organize them better.
10. To be able to right click a fuel tank to see how much fuel is left in that specific tank.
