Let us look at this verse again:
"He which testifieth these things saith, Surely I come quickly. Amen. Even so, come, Lord Jesus" (Rev.22:20).
It is impossible that John is speaking about anyone other than the Lord Jesus. That is because John says here that what is revealed to Him is based on the "testimony" of the Lord Jesus:
"The Revelation of Jesus Christ, which God gave unto him, to shew unto his servants things which must shortly come to pass; and he sent and signified it by his angel unto his servant John: Who bare record of the word of God, and of the testimony of Jesus Christ, and of all things that he saw" (Rev.1:1-2).
Do you get it?
John speaks of the "testimony" of Jesus Christ so therefore the one who "testifieth these things" can be none other than the Lord Jesus. And the last part of the same verse also proves that it is the Lord Jesus who testified of these things:
"He which testifieth these things saith, Surely I come quickly. Amen. Even so, come, Lord Jesus" (Rev.22:20).
You continue to just ignore these facts and I can understand why. They prove that the Lord Jesus is the
"Alpha and Omega, the beginning and the end." And since that fact proves that the Lord Jesus is God then you realize that you must somehow change the plain meaning of what is said at Revelation 22:20.