Multi-plane light conversion (MPLC) coherent beam combining (CBC) offers a promising approach for flexible optical field manipulation, overcoming the limitations of low energy utilization and poor beam quality in traditional CBC methods. However, its potential for generating diverse structured beams and the underlying design principles remain underexplored. In this work, theoretical model of MPLC-based CBC system is constructed to perform numerical investigation into the property and capability of MPLC optical field manipulation. Localized phase coding and vortex phase coding methods are proposed for mode mapping design to enhance the match between input and output modes. By using multi-dimensional evaluation metrics such as conversion efficiency (η), side-lobe suppression ratio (SSR), and phase matching degree (PMD), the performance of different coding strategies is systematically compared. The results show that although random coding yields an average efficiency of 92% for five multi-focus beams, both localized and vortex coding significantly improve output quality, achieving a superior average efficiency of 97.1%. Based on the proposed encoding methods, MPLC successfully produces 5 Laguerre-Gaussian (LG) beams, 5 geometric shapes, and 5 letter patterns with remarkably high average efficiencies, reaching 97.4%, 99.2%, and 96.5%, respectively, accompanied by high SSR (>14 dB) and PMD (>96%). Furthermore, a strategy for arbitrary beam shaping by decomposing the target field into a linear combination of orthogonal modes is proposed and confirmed using a 21-mode MPLC. At the same time, its flexibility and the resulting need for strong amplitude modulation of the laser array are discussed. Finally, the relationship between the number of supported modes and the required number of phase plates is also analyzed, showing that maintaining high efficiency for a larger number of modes necessitates a significant increase in the number of phase plates. This study effectively generates a wide range of structured beams with minimal stray light and high energy utilization, demonstrating that MPLC-based CBC is a powerful and versatile technique for high-efficiency, high-quality optical field manipulation. Future work should focus on optimizing the design to reduce the required number of planes, thereby enabling practical applications in high-power laser processing, optical communication, and quantum optics.