Developed a scalable feature for the Qiskit/qiskit repository that enables the addition of two sparse observables with a complex scalar multiplier, supporting more expressive quantum algorithm design and streamlined Hamiltonian construction. The implementation leveraged C and Rust programming, focusing on algorithm design and quantum computing concepts. The work included refining operator addition logic, ensuring stability by addressing double collection issues, and clarifying the semantics of scaled addition. Documentation and usage examples were updated to guide users, and the feature was iteratively improved through code review and collaboration with other contributors, resulting in a robust and well-documented enhancement to the codebase.