Have you considered to work the other way round?
1. 1st build the antenna in CST, simulate, obtain results.
2. If there’s need to, export FROM CST to MATLAB.
MATLAB is a powerful tool, but the built-in antennas library is still quite limited, while CST is a ready-to-use electromagnetic simulator that happens to have an antenna tool box.
Because I have worked with both CST for a patch antenna and with MATLAB Antenna Toolbox, out of curiosity, what problem/obstacle did you encounter that motivated changing simulator?
Regards, awaiting answer