How can moral acts not named in the Ten Commandments be left to individual conscience?

The Ten Commandments is just a summary, and Jesus summarized it further as loving God and loving your neighbor as yourself. The object of Jesus was not to make more laws but fewer, because obedience to morality is not based on whether a law says to do it or not. If my only motivation not to steal from you is that the law says do not steal, I am in big trouble and will not last long; but if my motivation is that I love and respect you as a human being, because I want to survive and thrive as God made me and I know you want the same, then I will give that to you. That is why Jesus said love even your enemies. If you read the rest of Exodus and Leviticus, you find all kinds of laws added to the Ten Commandments for particular situations; in Leviticus 18, for instance, it delineates not uncovering the nakedness of your father, mother, sister, and so on, and deliberately leaves one person off the list, which I think is on purpose, because that catches the person who is looking for a loophole to sin. And as Paul says in Romans 5:20, the law was given to expose your sin, not merely to keep you from it, so that you would repent and reach out to God for the grace to obey out of the right motivation, which is love and respect for another human being.