In ue4,you can't set up a MultiPosition ambient object directly. To settle this issue, you can create your own BP:
1、create a Blueprint object that inherits the Actor class.
2、add a variable(Public) ,this variable must be an array of Transforms.
3、use the variable you created and the API called SetMultiplePositions in your Blueprint object. (this requires that you know how to use this API function)
good luck!