Stunnedbygrace, I don't know you as a heretic hunter. This is new to me. I hope you will eventually come to understand that Trinitarianism is the false doctrine I oppose, not the Biblical doctrine on which we both can agree. I hope you can see that when we bring a particular narrative TO a text, we are going to see that narrative supported there. We find it there because we brought it with us. But this is not the way to learn our faith. We are seeking to know what Jesus and his apostles taught; we want them to give us the proper perspective and understanding.
If we bring Trinity doctrine to a narrow subset of a larger passage, we can find a way to interpret John's words to support Trinity doctrine. According to Trinity doctrine, what is the glory that Jesus had before the world began? Who knows? Whatever Jesus was like as the Second Person of the Trinity before he condescended to become a human being, he will return to that state.
But according to the rest of the upper-room discourse, what is the glory the Father is about to give to his son Jesus? Speaking of his crucifixion Jesus says, "“Now is the Son of Man glorified, and God is glorified in Him; if God is glorified in Him, God will also glorify Him in Himself, and will glorify Him immediately." In other words, both the father and the son will be glorified in the death, burial and resurrection of Jesus Christ. When Jesus rises to sit at the right hand of the Father, then Jesus will be glorified. In this context, Jesus is speaking of an exalted status that the Father will grant to the human being Jesus. And, this is very important, Jesus prays that the Father will grant this same exalted status to his apostles, who are also human beings.
"The glory which You have given Me I have given to them, that they may be one, just as We are one; I in them and You in Me, that they may be perfected in unity, so that the world may know that You sent Me, and loved them, even as You have loved Me. Father, I desire that they also, whom You have given Me, be with Me where I am, so that they may see My glory which You have given Me, for You loved Me before the foundation of the world." John 17:22-24
Unless we are willing to think that Jesus is asking the Father to elevate the Apostles to "Godhead" status, making them the fourth, fifth, sixth etc. member of the Godhead, then we must admit that glorification, in this context, refers to the nature, quality, and status of being morally perfect, leaders of Jesus' new kingdom. Jesus isn't asking God to restore him to his pre-human condition; he is asking the father to make him glorious by bestowing honor, and praise on him through the resurrection and ascension.