Given the superexponential scaling of these combinatorics-based analyses, the modular structure theorem can be employed to facilitate focused analyses where atom-connectivity permutations are considered for only a small subset of atoms in a larger system (e.g., as in Fig. ). Many approaches to this end are possible and it is worth noting that the Polytope Formalism of constitutional isomerism, when constrained by valence and limiting discussion to a single molecular entity, returns the same results as established methods for constitutional isomer enumeration. The following approach is broadly applicable to many chemical scenarios, especially where "bond walks" are key and range from simple cases of tautomerism to complex systems such as ion transport through transmembrane channels. Fig. illustrates how molecular systems can be partitioned where the subset of "active" atoms experiencing connectivity permutation can be further divided into two categories based upon their roles. We identify "mobile" atoms as "bonders" ℬ along with several bonding sites 𝒮 typically anchored within one or more larger molecular fragments.