Make the blueberry-sage syrup: Combine the sugar, water and blueberries in a medium saucepan over medium-high heat. Bring to a simmer, stirring. Muddle the berries well, mashing them in the pan. Add the sage and simmer 2 to 3 minutes. Let cool 10 minutes, then strain through a fine-mesh sieve, pressing on the solids. Refrigerate until cooled, about 1 hour.
Make the drink: Combine the spirits, orange sec, lime juice, bitters and 3/4 ounce of the blueberry-sage syrup in a cocktail shaker with ice. Shake well.
Strain the drink into a rocks glass (either rim the glass with merlot salt or sprinkle some on top for garnish). Add ice. Garnish with a flower, lime wheel or sage leaf.