The ThermalStorage:ChilledWater:Stratified has four nodes to be able to connect it on the source and use sides. The fact that you cannot do that in OpenStudio App seems like a bug to me. The WaterHeater objects used to have the same bug, at the time I wrote this measure that you could repurpose easily.bug.

Here's something you can do:

• Have a Plant loop with the chiller on the supply side, and two branches on the demand
• Put your storage tank across the loops, and an ideal heat exchanger.

I created an example model with the following code in terminal and then adding the chiller and HX in the OS App:

model = OpenStudio::Model::Model.new
source_plant = OpenStudio::Model::PlantLoop.new(model)
use_plant = OpenStudio::Model::PlantLoop.new(model)
tank = OpenStudio::Model::ThermalStorageChilledWaterStratified.new(model)
source_plant.addDemandBranchForComponent(tank)
use_plant.addSupplyBranchForComponent(tank)

Here's the 'Chiller ChW Loop':

Here's the 'Building ChW Loop'