You could also choose to have a microflow as datasource and then sort it in the microflow with a list operation. I guess it's sorted default in the order it's saved on the business server or by id default when retrieved from the database.
When retrieving by association it seems to choose the order in which the object were created. You can also to retrieve based on Xpath. When you do this, you can usually click on associations just as easily and sorting will be available for you: