In small microwavable bowl, melt white vanilla baking chips uncovered on High 30 to 45 seconds or until they can be stirred smooth. Stir in Cheerios cereal. Spread on waxed paper in single layer; top with sprinkles. Let stand until set, about 30 minutes. Break into pieces; reserve.
Meanwhile, place Chex cereal in large microwavable bowl.
In 2-cup glass measuring cup, melt butter uncovered on High about 30 seconds. Add brown sugar and maple syrup; microwave uncovered on High about 30 seconds or until mixture is boiling. Pour over Chex cereal in bowl, stirring until evenly coated.
Microwave Chex cereal mixture uncovered on High 3 to 4 minutes, stirring every minute, until mixture just begins to brown. Spread on waxed paper or foil. Cool completely, about 15 minutes. Break into bite-size pieces. Stir in miniature marshmallows and reserved Cheerios cereal pieces. Store in airtight container.