It (the Sabbath) is right in the middle of the Old Covenant, yes. But it is not one of the last six, being the moral code. The moral code is what we do to each other, otherwise called the royal law.
The first four Commandments mean,
1) God cannot be conceived or concluded for being,
2) God cannot be compared with any being,
3) God cannot be confused for being,
4) God cannot be mistaken for being.
The last seven Commandments mean,
4) Man must not forget it is God who made him and saved him,
5) Man must honour not himself but whom God had given honour to,
6) Man must not kill man in whose flesh God became his Life-Giver,
7) Man must not be unfaithful to his own because God is faithful to all,
8) Man must not think another’s goods is his and not God’s,
9) Man must not resent that others like himself are God’s people,
10) Man must not covet to be God or like others, like God.
The Ten Commandments is wholly about worshipping ONLY GOD.