After fashion designer Ulla Johnson launched her eponymous label in 1999, the brand swiftly became synonymous with an elegant slant of downtown bohemian chic. In the decades since, its reputation has continued to expand into a global retailer known for impeccable finishing, signature silhouettes, and devotion to perfection down to the smallest details. That is as much the case for her celebrated collections as it is for her standalone shops, which expanded to include a new location on Madison Avenue this month.