LYNN SHELTON, DIRECTOR OF MOVIES like Laggies and Your Sister’s Sister, has a knack for locating the approaching turns in characters’ lives; then she stands back, observing quietly but astutely as they figure out how to round them. In her wily, laid-back comedy Sword of Trust, a young woman, Jillian Bell’s Cynthia, inherits a Civil War–era sword from her grandfather, an item with a possibly unsavory past that she has no desire to own. With her high-strung partner Mary (Michaela Watkins), she heads off to a pawn shop. The mildly cantankerous owner, Mel (played by comedian and podcaster Marc Maron), hems and haws as he examines the hoary old weapon. He passes on it—only to have his hapless shop assistant Nathaniel (Jon Bass) inform him, after some random Googling, that…