The 20th annual Broadway Backwards benefit concert, celebrating the LGBTQ+ community via new twists on iconic songs in the musical theatre canon, plays Broadway's Gershwin Theatre March 23, and Playbill has a sneak peek at a number filmed during rehearsal. Above, watch "One Day More," the Act One finale from Claude-Michel Schönberg, Alain Boublil, and Herbert Kretzmer's Les Misérables. Leading the rousing song are…