Which of the "Ten Commands" is "love your neighbor as yourself?" What number is it in the list of ten on Moses's tablets?
Before you answer, please take not that loving your neighbor as yourself is not the same as not coveting your neighbor's stuff. For instance, one could be totally indifferent to ones neighbor, not wanting any of their possessions but also not caring at all about their problems or their fate.
Indeed, that's the exact situation presented in Jesus's parable of the Good Samaritan, the parable specifically answering the question of what it means to love your neighbor. After the unnamed traveler is robbed, stripped, and beaten, a priest and a Levite pass by without helping him. They are not violating the Tenth Commandment listed on Moses's tablets. What was there for them to covet? The traveler's nakedness? His injuries? Obviously not. Their inaction isn't due to coveting.
But, Jesus makes it clear, they were violating Jesus's admonition to love their neighbor. So, what number commandment is that? Where does that one appear on Moses's stone tablets?
I have to let the Scriptures explain what you so clearly presented—the understanding of the commands is that of love---subsequent laws illustrated that to love ones neighbour is to do good and not evil, understanding that another interpretation is to do to your neighbour the things that you would like done to yourself—so if you were a victim then you would like someone to help you.
Exo 23:4 "If you come across
your enemy's ox or donkey wandering off, be sure to take it back to him. If you see the donkey of someone
who hates you fallen down under its load, do not leave it there; be sure you help him with it.
So you are correct, in stating that it is not essential to help a fellow person, and is not decreed in the Decalogue---but it is a subsequent teaching, based on love, and compassion as Yahweh stated of himself---Exo 34:6 And he passed in front of Moses, proclaiming, "The LORD, the LORD, the compassionate and gracious God, slow to anger, abounding in love and faithfulness,
Exo 34:7 maintaining love to thousands, and forgiving wickedness, rebellion and sin. Yet he does not leave the guilty unpunished; he punishes the children and their children for the sin of the fathers to the third and fourth generation."
So to love your neighbor is not to lie steal, or covet his wife—so love is a practical application of the commands.
James_2:8 If you really keep the royal law found in Scripture, "Love your neighbour as yourself," you are doing right.
Romans_13:9 The commandments, "Do not commit adultery," "Do not murder," "Do not steal," "Do not covet," and whatever other commandment there may be,
are summed up in this one rule: "Love your neighbour as yourself."
Galatians_5:14 The entire law
is summed up in a single command: "Love your neighbour as yourself."
Take note the Decalogue was first given, then subsequent laws that would enhance the Decalogue.
It is said that we are created in the likeness of the Creator—but not everyone follows that characteristic. Some people become evil thereby denying the inherent good that we possess.