Jesus must have existed for everything to have been created
in him at the beginning
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Tonio, here is the role Jesus played in creation according to the Catholic Jerusalem Bible.
Proverbs 8 :
22 'Yahweh created me,
first-fruits of his fashioning, before the oldest of his works.
mce-anchor
23 From everlasting, I was firmly set, from the beginning, before the earth came into being.
30 I was beside the master craftsman, delighting him day after day, ever at play in his presence,
I don't know why this is missing in the KJV. However as you point out the NT makes it clear that after "Yahweh created me (Jesus)" , "all (other)things have been created
through him, and
unto him;" - Col 1:16.
It does not credit Jesus with being the Creator, but makes clear that God's Son existed "from the beginning, before the earth came into being".