So there are really 2 components to this question:
- Why can't I make a drop down field NOT 'required' in visual flow? and
- Why does each record in my sObject collection variable contain the previous record's dropdown choice as its default value?
I gather from Salesforce documentation that I should be able to make this field NOT required, but that option simply isn't visible. The field is not set as 'required' at the object level, or the page layout level.
The other part of this is that the flow iterates over a set of records in an sObject collection variable, using a loop. Each new record in the loop gets prepopulated with the dropdown value selected in the previous record. ie - if the previous answer was 'Yes', then the next record defaults to 'Yes', even if I set a default value for the field.
I have also tried using an assignment variable to set the dropdown value to a specific value, after each loop is performed, and before going to the screen again, but no success with that.