Knowledge-based CAD systems provide innovative solutions for automating design processes and enabling efficient, user-centric product customization. This paper presents a CAD configuration system for designing subway seat layouts, where users can input parameters such as train length, number of seats, and comfort settings. The system outputs a complete seat layout along with the maximum and standard seating capacities. This approach facilitates rapid visualization and evaluation of seat configurations, offering a valuable tool for generating and refining design concepts. The study outlines the development and implementation of this knowledge-based approach, focusing on the integration of parameter control into the CAD environment using Microsoft Excel and Autodesk iLogic. By externalizing parameter control, the system simplifies the process of visualizing and testing layout ideas. The results demonstrate the system's ability to handle complex interdependencies between design variables while providing intuitive customization options while keeping efforts for adaptation and maintenance of the system low.