There is a Q regarding the meaning of this verse. This Q is regarding the authenticity of the 'addition' - and what was intended by it. https://hermeneutics.stackexchange.com/questions/25129/what-is-meant-in-john-313-by-the-son-of-man-whos-in-heaven-yet-he-still-says?r=SearchResults&s=4|46.2592
Most modern translations seem to have the following for John 3:13
No one has ascended into heaven, but He who descended from heaven: the Son of Man
Then the KJ and a few others add, 'who is in heaven' so we get the following longer verse.
No one has ascended to heaven but He who came down from heaven, that is, the Son of Man who is in heaven.
The Alexandrian text omits this addition. Does it have veracity and/or what is the point of the addition?