What did Kant mean? I’ll tell ya. Transcendent means above ordinary experience. Kant saw structures dominating our minds, he put us at the service of those structures, and he referred to the study of those structures as Transcendental Idealism. It was fairly comfortable, a bit too safe, a tad fatalistic but he was able to say we were reasonable beings, because that's how we were structured, and that Morality, for example, was a product of one of those structures which in his view meant that somewhere in the mist there was a categorical Imperative which while it might not be able to tell us what being moral and upright actually was, nonetheless we people were leaning toward what Dr Martin Luther King later called Justice. This cozy sense of predestination was roundly, and in my view constructively rejected by Postmodernist thinkers.
