Quantity: Unity, Plurality, Totality
Quality: Reality, Negation, Limitation
Relation: Inherence, Causation, Community
Modality: Possibility, Existence, Necessity
When you look at the characterizations of these, Quantity and Relation are both quite clearly understood in TRS terms. Because of Relation, we can consider something like Substance, Law, System as a TRS triad, because in a sense relation establishes these as features of our understanding of the world; this makes a lot of sense, given how Kant understands each. Quality and Modality are trickier, but I think there's at least an argument that they should also be understand as a building triad.
But there are other cases in Kant. I think there's a very strong argument that Kant's three major formulations of the categorical imperative -- the Law of Nature formulation, the End in Itself formulation, and the Kingdom of Ends formulation form a TRS triad.
Kant, however, is not the only one who makes important use of TRS triads. Peirce does, as well. Peirce likes triads in general, and often discusses logic, so it is not surprising to find TRS triads in his work, but he very definitely builds them. The most obvious example, derived directly from Term, Proposition, Argument, is the Rheme, Dicent, Delome classification of signs; Peirce pretty clearly intends this to be a more general form of Term, Proposition, Argument, applicable to every kind of sign, and even will often use 'Argument' instead of 'Delome'. Given the analogies between this triad and the other two important triads of Qualisign, Sinsign, Legisign and Icon, Index, Symbol, these classifications seem to be TRS triads as well. If we can read Possibility, Existence, Necessity as a TRS triad for Peirce as well as Kant, this would clinch the argument, since many of Peirce's triads are structured in such a way as to be Possibility, Existence, Necessity triads of one form or another.
(One could, however, argue that Possibility, Existence, Necessity is a distinct kind of triad which can overlap with TRS triads. It's easy to relate Possibility as a Term-modality and Necessity as a System-modality, because that is closely tied to how we explain them to begin with -- the necessary is that which is found in all possibles -- but it's much harder to get a grasp on Existence as a Relation-modality, because Existence doesn't seem obviously reducible to just possibilities in relation. Existence is not really in between Possibility and Necessity; it is more fundamental than either, at least in how we think of them. Perhaps we are being too literal, though, and the real middle here is something that might be more accurately called Truth, in the ontological sense, as a relation between possibles.)
Various Links of Interest
* James Hankins, Pietas, at First Things
* Ashok discusses Gerard Manley Hopkins's "As Kingfishers Catch Fire"
* John Farrell reviews Mark Shea's The Church's Best-Kept Secret
* Patrick O'Donnell, Introducing the concept of rasa in Indian aesthetics and philosophy of art, at ReligiousLeftLaw.com
* Barbara Castle, Awakening to Virtue: Confessions of a Well-Read, Unlucky Good Girl
* Emrys Westacott, The Venerable Prejudice against Manual Labour
* John Marenbon, Why Read Boethius Today?
Ahmet Midhat Efendi, Felâtun Bey and Râkım Efendi
Declan Finn, Crusader