Combine rhubarb, water, and salt in a medium saucepan over medium-high heat. Bring to a boil, stirring occasionally. Reduce heat to medium-low and simmer, stirring occasionally, until rhubarb has broken down, 6 to 8 minutes. Mix in honey and continue stirring until mixture has thickened, 2 to 3 minutes. Remove from heat.
Line five 12- to 16-ounce jars in an assembly-line fashion. Place 2 tablespoons of the rhubarb mixture into the bottom of each jar. Top each with 2 tablespoons cracker crumbs and 2/3 cup yogurt in that order. Divide remaining rhubarb mixture and cracker crumbs over parfaits and top each with 1 tablespoon crushed walnuts. Seal jars and refrigerate until ready to eat.