Great question, and yes I never thought of asking it that way. But the immutable nature of Jesus has been well stated in Hebrew 13:8. “Jesus Christ is the same yesterday, today, and forever.”
Jesus, in taking on humanity, “emptied” Himself (Phil 2:7), was “made for a little while lower than the angels” (Heb 2:9, see also Ps 8:5), “increasing in wisdom and stature” (Luk 2:52). But all these are talking about Jesus’ human nature. And only serves to prove that He indeed take on humanity like all human.
The key to understanding Jesus and Trinity is:
Trinity = 1 Being 3 Persons, or 1 What 3 Whos
Jesus = 1 Person 2 Beings, or 1 Who 2 Whats
So His divine nature of the Trinity was not lost or faded when He took on the human nature. The divine nature, during His time on earth, was at best suppressed, as when He says “only the Father knows” (Matt 24:36). Because the human Jesus doesn’t know, but the divine Jesus is one w God, and of course knows what God knows.
I hope I’m making sense to you, and helped somewhat to understand.