@Facundo_Rodriguez_La see: Pattern Review: DMN Looping for Array Input
Is your collection already a java collection? if yes, then you can add it into the “collection” property on your multi-instance using a expression ${myCollection}. Otherwise if it is say “json”, you can parse it using SPIN (see camunda docs), and then do ${myCollection.elements()} in the collection property of the multi-instance. Then use the ElementVariable property to define your variable name that should hold the objects. When you access the variables within the execution of the user task, it would be something like execution.getVariable('myObject').prop('name').value() (in the case of spin json, otherwise it would be regular java Map accessors),