This paper offers a minimal theoretical model for the description of kinetic processes in organic nanocomposite systems, which allows taking into account the main factors typical to such systems. These key factors are: the electron-vibrational coupling, the influence of the matrix, the action of a low-frequency external electric field, and the existence of a long-lived coherence. The subject of the simulation is a trimer nanocluster embedded in a weakly ordered organic matrix. The three-center nanocluster of the bridge type is considered, which has two equivalent centers tunnel-coupled with the intermediate center. In the given paper, an extended Holstein Hamiltonian is applied and the wave function is chosen in a form of the electron-vibrational coherent package; then the canonical Hamilton equations are used. As a result, the system of differential equations concerning the chosen variational parameters was obtained. The proposed model is formulated so that to contain an optimal number of model parameters for a detailed description of considered factors and its interconnections. Next, the numerical simulations were performed in order to identify the electron localization regimes in the trimer nanocluster and to define the values of the controlling model parameters responsible for switching between the obtained regimes. Some of those results, which represent the most interesting regimes of the electron density distribution, are depicted graphically. Finally, these regimes are analyzed from the point of view of their possible application in nanoelectronics and nanobiology.