For sisters Pamela and Steph Katch, partners in the interior design firm Katch I.D., sketching plans for Upper East Side apartments in a Brooklyn loft with high ceilings and glorious natural light was one of the pleasures of owning their own business. “We loved Williamsburg,” says Steph, who relished the area’s edgy energy even if its location was a reach, in many ways, for much of their clientele. But last year, when the four-person firm was forced to move, the Katches found a new home in Manhattan at Fuigo, a group workplace specifically conceived for interior designers.