From the perspective of Swedenborgian Christians, who see God as one both in person and in essence, in whom is the Father, the Son, and the Holy Spirit, Isaiah 46:9 simply says what we believe: There is one and only one God.
Emanuel Swedenborg (1688–1772), our great theologian, devotes many pages, even whole chapters, to demonstrating that Jesus Christ, whom he simply calls "the Lord" was and is none other that God himself come to earth. Not the incarnation of some supposed eternal "God the Son," or some supposed second Person of the Godhead come to earth, so that he would represent only one-third of God, but the totality of God come to earth, just as Paul says:
For in him dwells all the fullness of the Godhead bodily (Colossians 2:9)
In a chapter in his book Doctrine of the Lord titled "The Lord Is God Himself, the Origin of and Subject of the Word" (§§37–44 of that book), Swedenborg quotes many passages to demonstrate that the same things that are attributed to the one God in the Old Testament are also attributed to Jesus in the New Testament. For example, in the Old Testament
I am Jehovah, and there is no Savior other than me. (Isaiah 43:11)
Am I not Jehovah? And there is no God other than me; and there is no Savior other than me. Look to me so that you may be saved, all you ends of the earth. (Isaiah 45:21–22)
I am Jehovah your God; there is no Savior other than me. (Hosea 13:4)
Compare those and others like them to these passages in the New Testament:
To you is born this day in the city of David a Savior, who is the Christ, the Lord. (Luke 2:11)
They said to the woman, "It is no longer because of what you said that we believe, for we have heard for ourselves, and we know that this is truly the Savior of the world." (John 4:42)
But it has now been revealed through the appearing of our Savior Jesus Christ, who abolished death and brought life and immortality to light through the gospel. (2 Timothy 1:10)
Again, in the Old Testament:
Thus says the Lord, the King of Israel, and his Redeemer, the Lord of hosts: I am the first, and I am the last; besides me there is no god. (Isaiah 44:6)
Listen to me, O Jacob, and Israel, whom I called: I am he; I am the first, and I am the last. (Isaiah 48:12)
And in the New Testament, as part of John's vision of the risen and glorified Jesus Christ:
When I saw him, I fell at his feet as though dead. But he placed his right hand on me, saying, "Do not be afraid; I am the first and the last." (Revelation 1:17)
Many more examples could be given of the New Testament referring to Jesus in the very same way that the Old Testament refers to God. Put this together with the many passages in both the Old Testament and the New Testament saying that there is only one God, and from a non-trinitarian standpoint that accepts Jesus as the incarnation of God, the only possible conclusion is that Jesus Christ is God himself come to earth.
This is why, after the Resurrection, Thomas addressed Jesus as:
My Lord and my God. (John 20:28)
In summary, once again, Isaiah 46:9 simply says exactly what we believe. No "interpretation" is necessary. Just read the words and believe them.
About the different names for God in the Bible, each of them has its own meaning relating to different attributes of God. But they all refer to the one God, who encompasses all attributes.