Combine the yogurt and cream cheese in a bowl and mix until creamy. Add the lemon juice, cinnamon, and sugar, then mix well. Stir in the gelatin and mix vigorously for 1 minute.
Pour the cream mixture into molds and refrigerate for at least 1 hour.
Place the cherries in a saucepan over medium-high heat and bring to a boil. Mix the cornstarch with a small amount of the cherry juice until smooth, then stir into the cherries. Simmer for 2-3 minutes until thickened. Remove from heat and allow to cool to room temperature (about 15-20 minutes).
Unmold the terrine onto a plate and serve with the cooled cherry compote. Garnish with lemon balm if desired.