Boston Ballet’s performances are magnificent, but awe-inspiring work also happens behind the scenes without a grand marquee. Case in point: Kathleen Mitchell, a longtime dancer with the San Francisco Ballet who’s now not only a faculty member at Boston Ballet, but the company’s shoe manager—a pivotal role when a single dancer can go through a hundred pairs per year. Tucked floors beneath the sunny rehearsal studios and filled to the ceiling with bespoke ballet slippers, Mitchell’s shoe closet features a wall of lockers into which she slips new shoes, each pair handcrafted and signed by the particular dancer’s preferred maker. It’s work that quite literally keeps the whole company on its toes.