Can it be said that whilst living on earth our Lord was both in heaven and yet on the way to heaven?
Yes; for as regards the function that is proper to the soul in heaven, this our Lord had, since He enjoyed fully this beatitude by the vision of the divine essence; but as regards the effect of this beatitude in His Body, this He had not as yet by a sort of miraculous suspension in view of our redemption; and this redundancy of the Soul's glory in the Body did not come about until after His Resurrection and Ascension into heaven (XV. 10).
Next - The Catechism of the Summa - Tertia Pars - X. OF THE CONSEQUENCES OF THE INCARNATION OF THE SON OF GOD; AND OF THE MANNER OF EXPRESSING IN WORDS THE TRUTHS THEREOF