Yu Donglai, founder of viral local supermarket chain Pangdonglai, became a star addition to a recent high-level economic symposium chaired by Chinese Premier Li Qiang, where economists and leading entrepreneurs gathered to discuss the country’s economic outlook. The retailer, headquartered in Xuchang, a small city in central China’s Henan province, has yet to expand its stores beyond the province. Despite an overall consumption slowdown in China and fierce competition from e-commerce platforms,...