This game is literally impossible to use at this point.
I am sure this has all been mentioned before, but:
Firstly: body properties like mass, density and radius just randomize each time one is changed. The game does not "simulate" these values, as I have seen written, it picks an average for the values you did not edit, and then does not allow you to change them. This makes building a custom body completely impossible.
Its simple maths. Two of the values should define the third.
Second: orbital elements are literally impossible to specify. If I change the eccentricity of an orbit, it either just assigns random values to all other orbital properties, or ignores my new eccentricity value. Why?
As far as bugs go, in a physical space simulation, these are game destroying. The game should never have been released with bugs like these.
The game is essentially useless at this point. The new gravity integrations and tweakable accuracy are great - or they would be if they were at all relevant. They have no use since the only thing you can do with any sort of certainty atm is hurl a moon into a planet and watch splosions happen.
These bugs need fixing very, very, very fast. There should at least be an option to turn off all the "simulation" of body mass, density and radius, and just allow users to input their own values. The orbital elements desperately need a stable means of input as well.
Until these bugs are fixed the game earns a solid 1/10. Completely useless at the moment. Harsh but true.