Line a rimmed baking sheet with parchment paper.
Combine yogurt, syrup, vanilla, and salt in a medium mixing bowl and stir until well combined. Stir in strawberry reserves and diced banana.
Pour mixture onto prepared baking sheet and spread it into a ½”-thick rectangle or oval. Freeze until firm, about 2 hours. Optional (you can do this before you freeze the yogurt or after is is frozen): melt the chocolate and coconut oil in a heat-proof bowl set over a pot of simmering water. Drizzle the melted chocolate over the yogurt with a spoon. After the chocolate has hardened (this should happen immediately), break into pieces and store in a covered container in the freezer. The bark should stay good in the freezer for up to 2 weeks.