A fundamental feature of WFEM is Bloch's theorem, which dictates a periodicity condition between boundary displacements and allows to compute the unit cell's Bloch wave basis. A larger periodicity scale can be identified by grouping several unit-cells together with the joint element interconnecting the waveguides, allowing to extend the formalism of quantum graph theory to complex waveguide networks. In this work, we introduce several formulations for the eigenproblem across the macro-unit-cell, including a naive transfer matrices product approach and a global Bloch transfer matrix approach. The latter is determined by expressing the joint element's boundary force equilibria in the unit-cell's wave basis, and is shown to optimize computation time and numerical errors. The same basis can also be used to establish a scattering relationship between outgoing and incoming waves across the joint element.