Is the New Heaven already in place to be seen or is it in process?
As I say in Heaven, there is an apparent physicality to the present Heaven, with thrones and sitting and standing and palm branches and the tree of life in the present paradise, etc.
Hebrews 12 speaks of the Heavenly City as apparently already existing in the present Heaven, but we don't know exactly how that works, except that it will be brought down to the New Earth for its eventual location:
“But you have come to Mount Zion, to the heavenly Jerusalem, the city of the living God. You have come to thousands upon thousands of angels in joyful assembly, to the church of the firstborn, whose names are written in heaven. You have come to God, the judge of all men, to the spirits of righteous men made perfect, to Jesus the mediator of a new covenant, and to the sprinkled blood that speaks a better word than the blood of Abel” (verses 22-24).